Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2015	Jan. 31, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Trading Symbol	FGEN
Entity Registrant Name	FIBROGEN INC
Entity Central Index Key	0000921299
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		62,074,139
Entity Public Float			$ 1,151.1

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 153,324	$ 165,455
Short-term investments	27,847	14,364
Accounts receivable ($4,455 and $5,033 from a related party)	15,405	13,453
Prepaid expenses and other current assets	3,988	4,966
Total current assets	200,564	198,238
Restricted cash	7,254	7,254
Long-term investments	131,720	144,269
Property and equipment, net	129,020	132,171
Other assets	2,016	1,596
Total assets	470,574	483,528
Current liabilities:
Accounts payable	6,521	4,551
Accrued liabilities ($2,045 and $4,594 to related parties)	47,932	48,985
Deferred revenue	12,728	9,218
Total current liabilities	67,181	62,754
Long-term portion of lease financing obligations	97,042	96,818
Product development obligations	15,085	16,465
Deferred rent	4,702	5,131
Deferred revenue, net of current	85,132	60,988
Other long-term liabilities	4,607	696
Total liabilities	$ 273,749	$ 242,852
Commitments and Contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.01 par value; 125,000 shares authorized at December 31, 2015 and 2014; no shares issued and outstanding at December 31, 2015 and 2014	$ 0	$ 0
Common stock, $0.01 par value; 225,000 shares authorized at December 31, 2015 and December 31, 2014; 61,985 and 59,046 shares issued and outstanding at December 31, 2015 and December 31, 2014	620	590
Additional paid-in capital	586,647	546,247
Accumulated other comprehensive loss	(1,651)	(3,149)
Accumulated deficit	(408,062)	(322,283)
Total stockholders’ equity	177,554	221,405
Non-controlling interests	19,271	19,271
Total equity	196,825	240,676
Total liabilities, stockholders’ equity and non-controlling interests	$ 470,574	$ 483,528

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Accounts receivable from related party	$ 4,455	$ 5,033
Accrued liabilities to related parties	$ 2,045	$ 4,594
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	125,000,000	125,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	225,000,000	225,000,000
Common stock, shares issued	61,985,000	59,046,000
Common stock, shares outstanding	61,985,000	59,046,000

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue:
License and milestone revenue (includes $18,701, $14,453 and $22,326 from a related party)	$ 148,093	$ 117,191	$ 94,961
Collaboration services and other revenue (includes $2,895, $3,535 and $3,335 from a related party)	32,735	20,410	7,209
Total revenue	180,828	137,601	102,170
Operating expenses:
Research and development	214,089	150,794	85,710
General and administrative	44,364	36,909	24,409
Total operating expenses	258,453	187,703	110,119
Loss from operations	(77,625)	(50,102)	(7,949)
Interest and other, net
Interest expense	(11,033)	(11,108)	(10,702)
Interest income and other, net	3,121	1,706	3,708
Total interest and other, net	(7,912)	(9,402)	(6,994)
Loss before income taxes	(85,537)	(59,504)	(14,943)
Provision for income taxes	242	0	0
Net loss	$ (85,779)	$ (59,504)	$ (14,943)
Net loss per share - basic and diluted	$ (1.42)	$ (3.17)	$ (1.13)
Weighted average number of common shares used to calculate net loss per share - basic and diluted	60,337	18,775	13,186

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
License and milestone revenue from a related party	$ 148,093	$ 117,191	$ 94,961
Collaboration services and other revenue from a related party	32,735	20,410	7,209
Astellas Agreement [Member]
License and milestone revenue from a related party	18,701	14,453	22,326
Collaboration services and other revenue from a related party	$ 2,895	$ 3,535	$ 3,335

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (85,779)	$ (59,504)	$ (14,943)
Other comprehensive income (loss):
Foreign currency translation adjustments	1,662	2,082	(665)
Available-for-sale investments:
Unrealized gain (loss) on investments, net of tax effect	30	(965)	(1,936)
Reclassification from accumulated other comprehensive loss	(194)	(758)	(740)
Net change in unrealized loss on available-for-sale investments	(164)	(1,723)	(2,676)
Other comprehensive income (loss), net of taxes	1,498	359	(3,341)
Comprehensive loss	$ (84,281)	$ (59,145)	$ (18,284)

Consolidated Statements of Redeemable Convertible Preferred Stock and Equity (Deficit) - USD ($) $ in Thousands	Total	Astra Zeneca [Member]	FibroGen Europe [Member]	Senior Preferred Stock [Member]	Senior Preferred Stock [Member] Astra Zeneca [Member]	Senior Preferred Stock [Member] FibroGen Europe [Member]	Junior Preferred Stock [Member]	Junior Preferred Stock [Member] Astra Zeneca [Member]	Junior Preferred Stock [Member] FibroGen Europe [Member]	Common Stock [Member]	Common Stock [Member] Astra Zeneca [Member]	Common Stock [Member] FibroGen Europe [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Astra Zeneca [Member]	Additional Paid-in Capital [Member] FibroGen Europe [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Other Comprehensive Loss [Member] Astra Zeneca [Member]	Accumulated Other Comprehensive Loss [Member] FibroGen Europe [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Astra Zeneca [Member]	Accumulated Deficit [Member] FibroGen Europe [Member]	Noncontrolling Interest [Member]	Noncontrolling Interest [Member] Astra Zeneca [Member]	Noncontrolling Interest [Member] FibroGen Europe [Member]
Balance at Dec. 31, 2012	$ (46,252)			$ 168,436			$ 136,313			$ 132			$ 37,606			$ (167)			$ (247,836)			$ 27,700
Balance, Shares at Dec. 31, 2012				38,340,182			46,460,057			13,167,138
Net loss	(14,943)			$ 0			$ 0			$ 0			0			0			(14,943)			0
Change in unrealized loss on investments	(2,676)			0			0			0			0			(2,676)			0			0
Foreign currency translation adjustments	(665)			0			0			0			0			(665)			0			0
Issuance of Series A Preferred to non-controlling interests	175			0			0			0			0			0			0			175
Stock options exercised	84			$ 0			$ 0			$ 0			84			0			0			0
Stock options exercised , Shares				0			0			34,126
Stock-based compensation	3,444			$ 0			$ 0			$ 0			3,444			0			0			0
Balance at Dec. 31, 2013	(60,833)			$ 168,436			$ 136,313			$ 132			41,134			(3,508)			(262,779)			27,875
Balance, Shares at Dec. 31, 2013				38,340,182			46,460,057			13,201,264
Net loss	(59,504)			$ 0			$ 0			$ 0			0			0			(59,504)			0
Change in unrealized loss on investments	(1,723)			0			0			0			0			(1,723)			0			0
Foreign currency translation adjustments	2,082			0			0			0			0			2,082			0			0
Stock options exercised	1,694			$ 0			$ 0			$ 5			1,689			0			0			0
Stock options exercised , Shares				0			0			539,971
Stock-based compensation	18,698			$ 0			$ 0			$ 0			18,698			0			0			0
Balance at Dec. 31, 2014	240,676			$ 0			$ 0			$ 590			546,247			(3,149)			(322,283)			19,271
Balance, Shares at Dec. 31, 2014				0			0			59,046,296
Conversion of preferred stock to common stock	$ 168,436		$ 0			$ 0			$ 0	$ 339		$ 10	$ 304,410		$ 8,594	$ 0		$ 0	$ 0		$ 0	$ 0
Conversion of preferred stock to common stock				$ (168,436)			$ (136,313)																	$ (8,604)
Conversion of preferred stock to common stock, shares						0			0	33,919,954		958,996
Conversion of preferred stock to common stock, shares	0			(38,340,182)			(46,460,057)			0			0			0			0			0
Initial Public Offering, net of underwriting discounts, commission and issuance costs	$ 151,826			$ 0			$ 0			$ 93			$ 151,733			$ 0			$ 0			$ 0
Initial Public Offering, net of underwriting discounts, commission and issuance costs, shares				0			0			9,315,000
Astra Zeneca private placement		$ 20,000			$ 0			$ 0			$ 11			$ 19,989			$ 0			$ 0			$ 0
Astra Zeneca private placement, Shares					0			0			1,111,111
Net loss	(85,779)			$ 0			$ 0			$ 0			0			0			(85,779)			0
Change in unrealized loss on investments	(164)			0			0			0			0			(164)			0			0
Foreign currency translation adjustments	1,662			0			0			0			0			1,662			0			0
Stock options exercised	10,112			$ 0			$ 0			$ 24			10,088			0			0			0
Stock options exercised , Shares				0			0			2,361,633
Stock-based compensation	27,681			$ 0			$ 0			$ 0			27,681			0			0			0
Balance at Dec. 31, 2015	196,825			$ 0			$ 0			$ 620			586,647			(1,651)			(408,062)			19,271
Balance, Shares at Dec. 31, 2015				0			0			61,985,079
Shares issued upon vesting of restricted stock units and purchases made under the employee stock purchase plan, shares				0			0			456,355
Shares issued upon vesting of restricted stock units and purchases made under the employee stock purchase plan	2,595			$ 0			$ 0			$ 5			2,590			0			0			0
True up of issuance costs related to initial public offering and common stock sold by FibroGen Europe	42			0			0			0			42			0			0			0
Warrants exercised	$ 0			$ 0			$ 0			$ 1			$ (1)			$ 0			$ 0			$ 0
Warrants exercised, Shares										120,795

Consolidated Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (85,779)	$ (59,504)	$ (14,943)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation	5,679	4,470	5,084
Amortization of premium on investments	2,997	658	841
Loss (gain) on disposal of property and equipment	98	(10)	(1)
Stock-based compensation	27,681	18,698	3,444
Realized gain on sales of available-for-sale securities	(203)	0	(301)
Changes in operating assets and liabilities:
Accounts receivable ($578, $979 and $2,772 from related party)	(1,952)	4,041	(8,711)
Prepaid expenses and other current assets	978	(1,628)	791
Other assets	(420)	(795)	(547)
Accounts payable	1,970	3,485	(2,041)
Accrued liabilities ($(2,549), $1,828 and $1,644 from related party)	(2,126)	18,878	11,307
Deferred revenue	27,654	33,557	30,885
Lease financing liability	627	814	690
Other long-term liabilities	4,225	(250)	(580)
Net cash provided by (used in) operating activities	(18,571)	22,414	25,918
Investing activities
Purchases of property and equipment	(1,977)	(8,118)	(6,806)
Proceeds from sale of property and equipment	2	10	2
Purchases of available-for-sale securities	(41,736)	(144,727)	0
Proceeds from sales of available-for-sale securities	15,342	0	16,582
Proceeds from maturities of available-for-sale securities	22,501	45,546	1,000
Net cash provided by (used in) investing activities	(5,868)	(107,289)	10,778
Financing activities
Borrowings under credit facility	0	0	11,500
Repayments under credit facility	0	0	(11,500)
Repayments of capital lease obligations	0	0	(329)
Repayments of lease liability	(403)	(403)	(403)
Proceeds from lease financing liability	0	0	553
Proceeds from convertible promissory note	0	0	600
Proceeds from non-controlling interest	0	0	175
Proceeds from initial public offering, net of underwriting discounts and commission costs	0	155,933	0
Proceeds from AstraZeneca private placement	0	20,000	0
Proceeds from issuance of common stock, net	12,749	1,697	84
Payments of deferred offering costs	0	(3,135)	0
Net cash provided by financing activities	12,346	174,092	680
Effect of exchange rate change on cash and cash equivalents	(38)	(94)	84
Net increase (decrease) in cash and cash equivalents	(12,131)	89,123	37,460
Cash and cash equivalents at beginning of period	165,455	76,332	38,872
Cash and cash equivalents at end of period	153,324	165,455	76,332
Supplemental cash flow information:
Interest payments	335	377	433
Purchases of property and equipment in accounts payable and accrued liabilities	931	280	1,655
Assets acquired under facility lease	0	0	3,067
Deferred offering costs recorded in accounts payable and accrued liabilities	$ 0	$ 974	$ 0

Consolidated Statement of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Cash Flows [Abstract]
Accounts receivable from related party	$ 578	$ 979	$ 2,772
Accrued liabilities from related party	$ 2,549	$ 1,828	$ 1,644

The Company

12 Months Ended

Dec. 31, 2015

Organization Consolidation And Presentation Of Financial Statements [Abstract]

The Company

1.	The Company

FibroGen, Inc. (“FibroGen” or the “Company”) was incorporated in 1993 in Delaware and is a research-based biopharmaceutical company focused on the discovery, development and commercialization of novel therapeutics agents to treat serious unmet medical needs. The Company’s focus in the areas of fibrosis and hypoxia-inducible factor (“HIF”) biology has generated multiple programs targeting various therapeutic areas. The Company’s most advanced product candidate, roxadustat, or FG-4592, is an oral small molecule inhibitor of HIF prolyl hydroxylases (“HIF-PHs”) in Phase 3 clinical development for the treatment of anemia in chronic kidney disease (“CKD”). FG-3019 is the Company’s monoclonal antibody in Phase 2 clinical development for the treatment of idiopathic pulmonary fibrosis (“IPF”), pancreatic cancer, Duchenne muscular dystrophy (“DMD”) and liver fibrosis. The Company has taken a global approach with respect to the development and future commercialization of its product candidates, and this includes development and commercialization in the People’s Republic of China (“China”).

On November 19, 2014, the Company closed the initial public offering (“IPO”) of its common stock. In its IPO, the Company sold 9,315,000 shares of its common stock at a public offering price of $18.00 per share. Net proceeds from the Company’s IPO and concurrent private placement were $171.8 million, after deducting underwriting discounts and commissions of $11.7 million and offering expenses of $4.1 million. Concurrent with the closing of the IPO, AstraZeneca AB (“AstraZeneca”), one of the Company’s collaboration partners, purchased shares of FibroGen common stock in a private placement at a price per share equal to the IPO price for an aggregate purchase price of $20.0 million. Upon the closing of the IPO, all outstanding shares of the Company’s convertible preferred stock automatically converted into 33,919,954 shares of common stock and 958,996 shares of FibroGen Europe convertible preferred stock were converted into shares of FibroGen common stock. The Company’s proceeds from the sale of the common stock sold in the concurrent private placement were $20.0 million.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of Significant Accounting Policies

Basis of Presentation and Liquidity

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The consolidated financial statements include the accounts of the Company, its wholly owned subsidiaries and its majority-owned subsidiaries, FibroGen Europe and FibroGen China Anemia Holdings, Ltd. (“FibroGen China”). All inter-company transactions and balances have been eliminated in consolidation. The Company operates in one segment — the discovery, development and commercialization of novel therapeutics to treat serious unmet medical needs. Based upon the current status of, and plans for, its product development, the Company believes that its existing cash and cash equivalents and its short term and long term investments, in addition to expected milestone payments related to certain collaboration agreements, will be adequate to satisfy the Company’s capital needs through at least the next twelve months. However, the process of developing and commercializing products requires significant research and development, preclinical testing and clinical trials, manufacturing arrangements as well as regulatory approvals. These costs, together with the Company’s general and administrative expenses, are expected to result in operating losses until the commercialization of the Company’s products or partner collaborations generate sufficient revenue to cover expenses. To achieve sustained profitability, the Company, alone or with others, must successfully develop its product candidates, obtain required regulatory approvals and successfully manufacture and market its products.

Foreign Currency Translation

The reporting currency of the Company and its subsidiaries is the United States (“U.S.”) dollar. The functional currency of FibroGen Europe is the Euro. The assets and liabilities of FibroGen Europe are translated to U.S. dollars at exchange rates in effect at the balance sheet date. All income statement accounts are translated at monthly average exchange rates. Resulting foreign currency translation adjustments are recorded directly in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity.

The functional currency of FibroGen, Inc. and all other subsidiaries is the U.S. dollar. Accordingly, monetary assets and liabilities in the non-functional currency of these subsidiaries are remeasured using exchange rates in effect at the end of the period. Revenues and costs in local currency are remeasured using average exchange rates for the period, except for costs related to those balance sheet items that are remeasured using historical exchange rates. The resulting remeasurement gains and losses are included within interest income and other, net in the consolidated statements of operations as incurred and have not been material for all periods presented.

Use of Estimates

The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Concentration of Credit Risk and Other Risks and Uncertainties

The Company is subject to risks associated with concentration of credit for cash and cash equivalents. A portion of cash on hand is invested in a diversified portfolio of investment grade corporate bonds issued by U.S. corporations as rated investment grade corporate bonds. Any remaining cash is deposited with major financial institutions in the U.S., Finland, China and the Cayman Islands. At times, such deposits may be in excess of insured limits. The Company has not experienced any loss on its deposits of cash and cash equivalents. Included in current assets are significant balances of accounts receivable as follows:

	As of December 31,
	2015			2014
Astellas Pharma Inc. (“Astellas”)—Related party		29	%		37	%
AstraZeneca AB (“AstraZeneca”)		71	%		63	%

The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, rapid technological change, the results of clinical trials and the achievement of milestones, market acceptance of the Company’s product candidates, competition from other products and larger companies, protection of proprietary technology, strategic relationships and dependence on key individuals.

Cash, Cash Equivalents and Restricted Cash

The Company considers all highly liquid investments with maturities of three months or less and that are used in the Company’s cash management activities at the date of purchase to be cash equivalents. Cash and cash equivalents include money market accounts, various deposit accounts, and money market funds. Restricted cash includes an irrevocable standby letter of credit as security deposit for a long-term property lease with the Company’s landlord. Restricted cash as of each of December 31, 2015, and 2014 totaled $7.3 million and $7.3 million, respectively. As of December 31, 2015, a total of $27.2 million of the Company’s cash and cash equivalents is held outside of the U.S. in the Company’s foreign subsidiaries to be used primarily for the Company’s China operations.

Investments

The Company classifies its investments as available-for-sale. Those investments with maturities less than 12 months are considered short-term investments. Those investments with maturities greater than 12 months are considered long-term investments. The Company’s investments classified as available-for-sale are recorded at fair value based upon quoted market prices at period end. Unrealized gains and losses that are deemed temporary in nature are recorded in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity.

A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the security. Premiums and discounts are amortized (accreted) over the life of the related security as an adjustment to its yield. Dividend and interest income are recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of investments sold.

Fair Value of Financial Instruments

Carrying amounts of certain of the Company’s financial instruments including cash equivalents, investments, receivables, accounts payable and accrued liabilities approximate fair value (refer to Note 4).

Property and Equipment

Property and equipment (except for costs of construction of certain long-lived assets — refer to Note 8) are recorded at cost and depreciated over their estimated useful lives using the straight-line method. Computer equipment, laboratory equipment, and furniture and fixtures are depreciated over three to five years. Leasehold improvements are recorded at cost and amortized over the term of the lease or their useful life, whichever is shorter.

Impairment of Long-Lived Assets

The Company continually evaluates whether events or circumstances have occurred that indicate that the estimated remaining useful life of its long-lived assets may warrant revision or that the carrying value of these assets may be impaired. If the Company determines that an impairment trigger has been met, the Company evaluates the realizability of its long-lived assets based on a comparison of projected undiscounted cash flows from use and eventual disposition with the carrying value of the related asset. Any write-downs (which are measured based on the difference between the fair value and the carrying value of the asset) are treated as permanent reductions in the carrying amount of the assets (asset group). Based on this evaluation, the Company believes that, as of each of the balance sheet dates presented, none of the Company’s long-lived assets were impaired.

Revenue Recognition

Substantially all of the Company’s revenues to date have been generated from its collaboration agreements.

The Company’s collaboration agreements include multiple deliverables, and the Company therefore follows the guidance in Accounting Standards Codification (“ASC”) Topic 605-25, Revenue Recognition—Multiple-Element Arrangements, (“ASC 605-25”), which:

·	provides guidance on how deliverables in an arrangement should be separated and how the arrangement consideration should be allocated to the separate units of accounting;

·	requires an entity to determine the selling price of a separate deliverable using a hierarchy of (i) vendor-specific objective evidence (“VSOE”), (ii) third-party evidence (“TPE”), or (iii) best estimate of selling price (“BESP”); and

·	requires the allocation of the arrangement consideration, at the inception of the arrangement, to the separate units of accounting based on relative selling price.

The Company evaluates all deliverables within an arrangement to determine whether or not they provide value on a stand-alone basis. Based on this evaluation, the deliverables are separated into units of accounting. The arrangement consideration that is fixed or determinable at the inception of the arrangement is allocated to the separate units of accounting based on their relative selling prices. Significant judgment may be required in determining whether a deliverable provides stand-alone value, determining the amount of arrangement consideration that is fixed or determinable, and estimating the stand-alone selling price of each unit of accounting.

To date, the Company has determined that the selling price for the deliverables within its collaboration agreements should be determined using BESP, as neither VSOE nor TPE is available. The process for determining BESP involves significant judgment on the Company’s part and includes consideration of multiple factors, including assumptions related to the market opportunity and the time needed to commercialize a product candidate pursuant to the relevant license, estimated direct expenses and other costs, which include the rates normally charged by contract research and contract manufacturing organizations for development and manufacturing obligations, and rates that would be charged by qualified outsiders for committee services.

For each unit of accounting identified within an arrangement, the Company determines the period over which the deliverables are provided and the performance obligation is satisfied. Service revenue is recognized using a proportional performance method. Direct labor hours or full time equivalents are typically used as the measurement of performance. Revenue may be recognized using a straight line method when performance is expected to occur roughly consistently over a period of time.

Payments or reimbursements resulting from the Company’s research and development efforts for those arrangements where such efforts are considered as deliverables are recognized as the services are performed and are presented on a gross basis. To the extent payments are required to be made to the collaboration partners pursuant to research and development efforts, those costs are charged to research and development using the guidance pursuant to ASC 605-250, Customer Payments and Incentives, which states that cash consideration given by a vendor to a customer is presumed to be a reduction of the selling prices unless the vendor receives an identifiable benefit in exchange for the consideration that is sufficiently separable from the recipient’s purchase of the vendor’s products, and the vendor can reasonably estimate the fair value of the benefit.

Each of the Company’s collaboration agreements includes milestones for which the Company follows ASC 605-28, Revenue Recognition—Milestone Method (“ASC 605-28”). ASC 605-28 establishes the milestone method as an acceptable method of revenue recognition for certain contingent event-based payments under research and development arrangements. Under the milestone method, a payment that is contingent upon the achievement of a substantive milestone is recognized in its entirety in the period in which the milestone is achieved. A milestone is an event (i) that can only be achieved based in whole or in part on either the Company’s performance or on the occurrence of a specific outcome resulting from the Company’s performance, (ii) for which there is substantive uncertainty at the date the arrangement is entered into that the event will be achieved and (iii) that would result in additional payments being due to the Company. Determining whether a milestone is substantive is a matter of judgment and that assessment must be made at the inception of the arrangement. Milestones are considered substantive when the consideration earned from the achievement of the milestone is (i) commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the item delivered as a result of a specific outcome resulting from the Company’s performance to achieve the milestone, (ii) relates solely to past performance and (iii) is reasonable relative to all deliverables and payment terms in the arrangement. Payments for achieving milestones which are not considered substantive are treated as additional arrangement consideration and are allocated following the relative selling price method previously described.

Research and Development Expenses

Research and development expenses consist of independent research and development costs and the gross amount of costs associated with work performed under collaboration agreements. Research and development costs include employee-related expenses, expenses incurred under agreements with clinical research organizations (“CROs”), other clinical and preclinical costs and allocated direct and indirect overhead costs, such as facilities costs, information technology costs and other overhead. All research and development costs are expensed as incurred.

Clinical Trial Accruals

Clinical trial costs are a component of research and development expenses. The Company accrues and expenses clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research organizations and clinical sites. The Company determines the costs to be recorded based upon validation with the external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services.

General and Administrative Expenses

General and administrative expenses consist primarily of employee-related expenses for executive, operational, finance, legal and human resource functions. Other general and administrative expenses include facility-related costs and professional service fees, other outside services, recruiting fees and expenses associated with obtaining and maintaining patents.

Income Taxes

The Company utilizes the asset and liability method of accounting for income taxes which requires the recognition of deferred tax assets and liabilities for expected future consequences of temporary differences between the financial reporting and income tax bases of assets and liabilities using enacted tax rates. Management makes estimates, assumptions and judgments to determine the Company’s provision for income taxes and also for deferred tax assets and liabilities, and any valuation allowances recorded against the Company’s deferred tax assets. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent the Company believes that recovery is not likely, the Company must establish a valuation allowance.

The calculation of the Company’s current provision for income taxes involves the use of estimates, assumptions and judgments while taking into account current tax laws, interpretation of current tax laws and possible outcomes of future tax audits. The Company has established reserves to address potential exposures related to tax positions that could be challenged by tax authorities. Although the Company believes its estimates, assumptions and judgments to be reasonable, any changes in tax law or its interpretation of tax laws and the resolutions of potential tax audits could significantly impact the amounts provided for income taxes in the Company’s consolidated financial statements.

The calculation of the Company’s deferred tax asset balance involves the use of estimates, assumptions and judgments while taking into account estimates of the amounts and type of future taxable income. Actual future operating results and the underlying amount and type of income could differ materially from the Company’s estimates, assumptions and judgments thereby impacting the Company’s financial position and results of operations.

The Company has adopted ASC 740-10, Accounting for Uncertainty in Income Taxes, that prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of uncertain tax positions taken or expected to be taken in the Company’s income tax return, and also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure and transition.

The Company includes interest and penalties related to unrecognized tax benefits within income tax expense in the Consolidated Statements of Operations.

Stock-Based Compensation

The Company maintains equity incentive plans under which incentive and nonqualified stock options are granted to employees and non-employee consultants. Compensation expense relating to non-employee stock options has not been material for the years ended December 31, 2015, 2014 and 2013.

The Company measures and recognizes compensation expense for all stock options and restricted stock units (“RSUs”) granted to its employees and directors based on the estimated fair value of the award on the grant date. The Company uses the Black-Scholes valuation model to estimate the fair value of stock option awards. The fair value is recognized as expense, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award, on a straight-line basis. The Company believes that the fair value of stock options granted to non-employees is more reliably measured than the fair value of the services received. As such, the fair value of the unvested portion of the options granted to non-employees is re-measured each period. The resulting increase in value, if any, is recognized as expense during the period the related services are rendered on a straight-line basis. The determination of the grant date fair value of options using an option pricing model is affected by the Company’s estimated Common Stock fair value and requires management to make a number of assumptions including the expected life of the option, the volatility of the underlying stock, the risk-free interest rate and expected dividends.

Comprehensive Income (Loss)

The Company is required to report all components of comprehensive income (loss), including net loss, in the consolidated financial statements in the period in which they are recognized. Comprehensive income (loss) is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources, including unrealized gains and losses on investments and foreign currency translation adjustments. Comprehensive gains (losses) have been reflected in the consolidated statements of comprehensive income (loss) for all periods presented.

Recently Issued and Adopted Accounting Guidance

In November 2015, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes. This guidance requires reporting entities to classify deferred income taxes as non-current on the consolidated balance sheets, which simplifies the presentation of deferred income taxes. This guidance is effective for annual reporting periods beginning after December 15, 2016, and interim periods within those annual periods, with early adoption permitted. The Company early adopted this guidance effective December 31, 2015 on a prospective basis. The adoption of this guidance had no impact on the Company’s financial position, results of operations or cash flows.

Recently Issued Accounting Guidance Not Yet Adopted

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). Under this guidance, an entity is required to recognize right-of-use assets and lease liabilities on its balance sheet and disclose key information about leasing arrangements. This guidance offers specific accounting guidance for a lessee, a lessor and sale and leaseback transactions. Lessees and lessors are required to disclose qualitative and quantitative information about leasing arrangements to enable a user of the financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. This guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period, and requires a modified retrospective adoption, with early adoption permitted. The Company is currently evaluating the impact on its consolidated financial statements upon the adoption of this guidance.

In January 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall (Subtopic 825-10), which requires equity investments that are not accounted for under the equity method of accounting to be measured at fair value with changes recognized in net income, simplifies the impairment assessment of certain equity investments, and updates certain presentation and disclosure requirements. This guidance is effective for annual reporting periods beginning after December 15, 2017 and interim periods within those annual periods. The Company is currently evaluating the impact on its consolidated financial statements upon the adoption of this guidance.

In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements - Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. This guidance requires management to evaluate, at each interim and annual reporting period, whether there are conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date the financial statements are issued, and provide related disclosures. This guidance will be effective for annual period ending after December 15, 2016, and for annual and interim periods thereafter. Early adoption is permitted. The Company does not expect a material impact on its consolidated financial statements upon the adoption of this guidance.

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes the revenue recognition requirements in ASC 605, Revenue Recognition. This guidance is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. This guidance can be adopted either retrospectively to each prior reporting period presented, or retrospectively with a cumulative-effect adjustment recognized as of the date of adoption. The original effective date of this guidance for public entities was for annual reporting periods beginning after December 15, 2016. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606), to defer the effective date of this guidance by one year, to the annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. A reporting entity may choose to early adopt the guidance as of the original effective date. The Company does not anticipate an early adoption, and is currently evaluating the impact on its consolidated financial statements upon the adoption of this guidance.

Collaboration Agreements

12 Months Ended

Dec. 31, 2015

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaboration Agreements

3.	Collaboration Agreements

Astellas Agreements

Japan Agreement

In June 2005, the Company entered into a collaboration agreement with Astellas Pharma Inc. (“Astellas”) for the development and commercialization (but not manufacture) of roxadustat for the treatment of anemia in Japan (“Japan Agreement”). Under this agreement, Astellas paid license fees and other consideration totaling $40.1 million (such amounts were fully received as of February 2009). The Japan Agreement also provides for additional development and regulatory approval milestone payments up to $117.5 million, a commercial sales related milestone of $15.0 million and additional consideration based on net sales (as defined) in the low 20% range after commercial launch. A clinical milestone payment of $12.5 million was received in 2013. The Company evaluated the criteria under ASC 605-28 and concluded that the aforementioned milestone was substantive.

Europe Agreement

In April 2006, the Company entered into a separate collaboration agreement with Astellas for the development and commercialization of roxadustat for the treatment of anemia in Europe, the Middle East, the Commonwealth of Independent States and South Africa (“Europe Agreement”). Under the terms of the Europe Agreement, Astellas paid license fees and other upfront consideration totaling $320.0 million (such amounts were fully received as of February 2009). The Europe Agreement also provides for additional development and regulatory approval milestone payments up to $425.0 million. Clinical milestone payments of $40.0 million and $50.0 million were received in 2010 and 2012, respectively. The Company evaluated the criteria under ASC 605-28 (and concluded that each of those milestones was substantive. Under the Europe Agreement, Astellas committed to fund 50% of joint development costs for Europe and North America, and all territory-specific costs. The Europe Agreement also provides for tiered payments based on net sales of product (as defined) in the low 20% range.

AstraZeneca Agreements

U.S./Rest of World Agreement

Effective July 30, 2013, the Company entered into a collaboration agreement with AstraZeneca for the development and commercialization of roxadustat for the treatment of anemia in the U.S. and all other countries in the world, other than China, not previously licensed under the Astellas Europe and Astellas Japan Agreements (“U.S./RoW Agreement”). It also excludes China, which is covered by a separate agreement with AstraZeneca described below. Under the terms of the U.S./RoW Agreement, AstraZeneca has agreed to pay upfront, non-contingent and time-based payments totaling $374.0 million, which the Company expects to receive in various amounts through June 2016, of which $312.0 million was received as of December 31, 2015. The remaining payment of $62.0 million is contingent upon the occurrence of a specified event and accordingly is also not considered fixed or determinable. In addition, the U.S./RoW Agreement also provides for development and regulatory approval based milestone payments of up to $550.0 million, which include potential future indications which the companies choose to pursue, and commercial related milestone payments of up to $325.0 million. During the second quarter of 2015, the Company received a $15.0 million development milestone payment as a result of the finalization of its two audited pre-clinical carcinogenicity study reports. The Company evaluated the criteria under ASC 605-28 and concluded that the aforementioned milestone was substantive.

Under the U.S./RoW Agreement, the Company and AstraZeneca will share equally in the development costs of roxadustat not already paid for by Astellas, up to a total of $233.0 million. Any additional development costs incurred by FibroGen during the development period in excess of the $233.0 million (aggregated spend) will be fully reimbursed by AstraZeneca. AstraZeneca will pay the Company tiered royalty payments on AstraZeneca’s future net sales (as defined in the agreement) of roxadustat in the low 20% range. In addition, the Company will receive a transfer price for delivery of commercial product based on a percentage of AstraZeneca’s net sales (as defined in the agreement) in the low- to mid-single digit range.

China Agreement

Effective July 30, 2013, the Company (through its subsidiaries affiliated with China) entered into a collaboration agreement with AstraZeneca for the development and commercialization (but not manufacture) of roxadustat for the treatment of anemia in China (“China Agreement”). Under the terms of the China Agreement, AstraZeneca agreed to pay upfront consideration totaling $28.2 million (such amounts were fully received as of March 31, 2014). In addition, the China Agreement provides for AstraZeneca to pay regulatory approval and other approval related milestones of up to $161.0 million. The China Agreement also provides for sales related milestone payments of up to $167.5 million and contingent payments of $20.0 million related to possible future compounds. The China Agreement is structured as a 50/50 profit or loss share (as defined) and provides for joint development costs (including capital and equipment costs for construction of the manufacturing plant in China), to be shared equally during the development.

Accounting for the Astellas Agreements

For each of the Astellas agreements, the Company has evaluated the deliverables within the respective arrangements and has separated them into various units of accounting.

Deliverables that did not provide standalone value have been combined with other deliverables to form a unit of accounting that collectively has standalone value, with revenue being recognized on the combined unit of accounting, rather than the individual deliverables. There are no right-of-return provisions for the delivered items in the Astellas agreements.

For the Astellas agreements, the Company allocated arrangement consideration to various units of accounting based on BESP of each deliverable within each unit of accounting using the relative selling price method as the Company did not have VSOE or TPE of selling price for such deliverables. Arrangement consideration includes non-contingent upfront payments of $360.1 million and cumulative co-development billings of $124.1 million (for Europe Agreement) as of December 31, 2015.

For the technology license under the Japan Agreement and Europe Agreement, BESP was determined primarily by using the discounted cash flow (“DCF”) method, which aggregates the present value of future cash flows to determine the valuation as of the effective date of each of the agreements. The DCF method involves the following key steps: 1) the determination of cash flow forecasts and 2) the selection of a range of comparative risk-adjusted discount rates to apply against the cash flow forecasts. The discount rates selected were based on expectations of the total rate of return, the rate at which capital would be attracted to the Company and the level of risk inherent within the Company. The discounts applied in the DCF analysis ranged from 17.5% to 20.0%. The Company’s cash flow forecasts were derived from probability-adjusted revenue and expense projections by territory. Such projections included consideration of taxes and cash flow adjustments. The probability adjustments were made after considering the likelihood of technical success at various stages of clinical trials and regulatory approval phases. BESP also considered certain future royalty payments associated with commercial performance of the Company’s compounds, transfer prices and expected gross margins.

The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows:

License to the Company’s technology existing at the effective date of the agreements. For both of the Astellas agreements, the license was delivered at the beginning of the agreement terms, or when the agreements were signed, and any contingencies had been removed. In both cases, the Company concluded at the time of the agreement that its collaboration partner, Astellas, would have the knowledge and capabilities to exploit the licenses without the Company’s further involvement. However, the Japan Agreement with Astellas has contractual limitations that might affect Astellas’ ability to exploit the license and therefore, potentially, the conclusion as to whether the license provides stand-alone value. In the Japan agreement, Astellas does not have the right to manufacture commercial supplies of the drug. In order to determine whether this characteristic of the agreement should lead to a conclusion that the license did not have stand-alone value, the Company considered the intent of the parties and the substantive reasons that led to that feature of the agreement.

Manufacturing rights. In the case of the Japan Agreement, the Company retained manufacturing rights largely because of the way the parties chose for FibroGen to be compensated under the agreement. At the time the agreement was signed, the Company believed that it was more advantageous upon commercialization to have a transfer price revenue model in place as opposed to a traditional sales-based model. The Company and Astellas could have structured the arrangement with a transfer of manufacturing rights and compensated the Company through a royalty or other feature without significantly diminishing the prospects of the drug product. Therefore, the Company determined that the license in Japan provides stand-alone value to the customer despite the lack of manufacturing rights.

License to the Company’s technology developed during the term of the agreement and development (referred to as “when and if available”) and information sharing services. These deliverables are generally delivered throughout the term of the agreements and are recognized as revenue as the services are provided.

Co-development services (Europe Agreement). This deliverable relates to co-development services that were reasonably expected to be performed by the Company at the time the collaboration agreement was signed. Revenue is recognized as reimbursements for such co-development services are earned. The period related to this deliverable represented the Company’s determination of the non-contingent performance period, which was estimated to be 36 months for the Europe Agreement from the signing of the agreement. There was no provision for co-development services in the Japan agreement.

Manufacturing of clinical supplies of products. This deliverable is satisfied as supplies for clinical product are delivered for use in the Company’s clinical trial programs during the development period, or pre-commercialization period. Revenue is recognized based on the estimated proportion of the development services performed during the development period. These estimates are made at the beginning of each accounting period and will likely change throughout the course of the terms of both agreements. As new information related to these estimates becomes available, the Company may adjust the timing of revenue recognition related to this unit of accounting.

Manufacturing commercial supplies of products. This deliverable is satisfied and revenue is recognized as supplies are shipped for commercial use during the commercialization period. As this deliverable is considered a contingent deliverable, it is outside the scope of the initial allocation of upfront and other consideration.

·	Committee service. This deliverable is satisfied and revenue is recognized throughout the course of the various agreements as meetings are attended.

Any consideration received for each Astellas agreement after the initial proceeds on the agreement signing date were also (and will be also) allocated to the various units of accounting above per agreement using the relative selling price method under ASC 605-25.

Under the Japan Agreement, the Company is also eligible to receive from Astellas an aggregate of approximately $132.5 million in potential milestone payments, comprised of (i) up to $22.5 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $95.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, and (iii) up to approximately $15.0 million in milestone payments upon the achievement of specified commercial sales milestone.

Under the Europe Agreement, the Company is also eligible to receive from Astellas an aggregate of approximately $425.0 million in potential milestone payments, comprised of (i) up to $90.0 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $335.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, including up to $25.0 million in milestone payments in connection with receipt of marketing approval in Russia.

Accounting for the AstraZeneca Agreements

The Company evaluated whether the U.S./RoW and China Agreements should be accounted for as a single arrangement and concluded that the agreements should be accounted for as a single arrangement with the presumption that two or more agreements executed with a single customer at or around the same time should be presumed to be a single arrangement. Accordingly, upfront and other non-contingent arrangement consideration received and to be received has been and will be pooled together and allocated to each of the units of accounting in both the U.S./RoW and China Agreements based on their relative fair values.

The Company evaluated the deliverables within the arrangement and has separated them into various units of accounting. Deliverables that did not provide stand-alone value have been combined with other deliverables to form a unit of accounting that collectively has stand-alone value, with revenue being recognized on the combined unit of accounting, rather than the individual deliverables. There are no right-of-return provisions for the delivered items in the agreements.

For the technology license under the AstraZeneca U.S./RoW Agreement, BESP was determined based on a two-step process. The first step involved determining an implied royalty rate that would result in the net present value of future cash flows to equal to zero (i.e. where the implied royalty rate on the transaction would equal the target return for the investment). This results in an upper bound estimation of the magnitude of royalties that a hypothetical acquirer would reasonably pay for the forecasted cash flow stream. The Company’s cash flow forecasts were derived from probability-adjusted revenue and expense projections. Such projections included consideration of taxes and cash flow adjustments. The probability adjustments were made after considering the likelihood of technical success at various stages of clinical trials and regulatory approval phases. The second step involved applying the implied royalty rate, which was determined to be 40%, against the probability-adjusted projected net revenues by territory and determining the value of the license as the net present value of future cash flows after adjusting for taxes. The discount rate utilized was 17.5%.

U.S./RoW Agreement:

The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows:

License to the Company’s technology existing at the effective date of the agreements. For the U.S./RoW Agreement, the license was delivered at the beginning of the agreement terms as all contingencies had been removed. The Company concluded that AstraZeneca has the knowledge and capabilities to exploit the U.S./RoW license without the Company’s further involvement.

Co-development services. This deliverable relates to co-development services which were reasonably expected to be performed by the Company at the time the Agreement was signed. Revenue is recognized as reimbursements for such co-development services are earned. The period related to this deliverable represented the Company’s determination of the non-contingent performance period, which was estimated to be 65 months from the signing of the U.S./RoW Agreement.

Manufacturing of clinical supplies of products. This deliverable is satisfied as supplies for clinical product are delivered for use in the Company’s clinical trial programs during the development period, or pre-commercialization period. Revenue is recognized based on the estimated proportion of the development services performed during the development period. These estimates are made at the beginning of each accounting period and will likely change throughout the course of the agreements. As new information related to these estimates becomes available, the Company may adjust the timing of revenue recognition related to this unit of accounting.

·	Committee service. This deliverable is satisfied and revenue is recognized throughout the course of the various agreements as meetings are attended.

Under the terms of the U.S./RoW Agreement, AstraZeneca has agreed to pay upfront, non-contingent and time-based payments totaling $374.0 million, which we expect to receive in various amounts through June 2016, of which $82.0 million was received as of December 31, 2013 and was determined to be fixed and determinable upon the execution of the collaboration agreement. Out of the remaining payments of $292.0 million, which are contractually due, $230.0 million have extended payment terms and, accordingly, were not considered to be fixed or determinable upon the execution of the agreement. As such, for these remaining payments, the amount of revenue recognized is limited to the amount of cash consideration received; additionally, for each of the amounts received, the amount of revenue recognized is determined on the basis of applying the relative selling price method to each of the units of accounting underlying the agreement. Further, $62.0 million of the remaining payment is contingent upon the occurrence of a specified event and accordingly is also not considered fixed or determinable.

Under the U.S./RoW Agreement, the Company is also eligible to receive from AstraZeneca an aggregate of approximately $875.0 million in potential milestone payments, comprised of (i) up to $65.0 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $325.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, (iii) up to $160.0 million in non-substantive deferred approval milestone, which would be paid if certain competitors do not launch an HIF compound in the U.S. on or before January 1, 2023 and (iv) up to approximately $325.0 million in milestone payments upon the achievement of specified commercial sales events.

China Agreement:

The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows:

License to the Company’s technology existing at the effective date of the agreement. The license was delivered at the beginning of the agreement term as all contingencies had been removed. However, the China Agreement with AstraZeneca has contractual limitations that might affect AstraZeneca’s ability to exploit the license and therefore, potentially, the conclusion as to whether the license provides stand-alone value. In the China Agreement, AstraZeneca does not have the right to manufacture commercial supplies of the drug. In order to determine whether this characteristic of the arrangement should lead to a conclusion that the license did not have stand-alone value, the Company considered the intent of the parties and the substantive reasons that led to that feature of the agreement.

For the China Agreement, the Company retained manufacturing rights as an essential part of a strategy to pursue domestic regulatory pathway for product approval which requires the regulatory licensure of the manufacturing facility in order to commence commercial shipment. The prospects for the collaboration as a whole would have been substantially different had manufacturing rights been provided to AstraZeneca. Because the retention of manufacturing rights by the Company was a significant factor in the collaboration strategy, rather than simply a mechanism to properly compensate FibroGen, management concluded that the license and development services do not have stand-alone value apart from the manufacturing rights. Accordingly, all the deliverables identified, including co-development services, under the China Agreement have been treated as a single unit of account and all revenue allocable to this unit of account is deferred until delivery of commercial drug product has begun. Upon commencement of delivery of commercial drug product, revenue would be recognized in a pattern consistent with estimated deliveries of the commercial drug product.

Under the terms of the China Agreement, AstraZeneca agreed to pay upfront consideration totaling $28.2 million, of which $16.2 million was received as of December 31, 2013 and was determined to be fixed and determinable upon the execution of the collaboration agreement. The remainder of the upfront payments of $12.0 million had extended payment terms and, accordingly, is not considered to be fixed or determinable upon the execution of the agreement. This payment of $12.0 million was received as of March 31, 2014.

Under the China Agreement, the Company is also eligible to receive from AstraZeneca an aggregate of approximately $328.5 million in potential milestone payments, comprised of (i) up to $15.0 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $146.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, and (iii) up to approximately $167.5 million in milestone payments upon the achievement of specified commercial sales events.

As the Company is accounting for both the U.S./RoW and China Agreements as one arrangement, any consideration received after the initial proceeds on the agreement signing date were also (and will be also) allocated to the various units of accounting above using the relative selling price method under ASC 605-25.

Summary of revenue recognized under the collaboration agreements

The table below summarizes the accounting treatment for the various deliverables pursuant to each of the Astellas and AstraZeneca agreements. License amounts identified below are included in the “License and milestone revenue” line item in the consolidated statements of operations. All other elements identified below are included in the “Collaboration services and other revenue” line item in the consolidated statements of operations.

Amounts recognized as revenue under the Japan Agreement are shown below (in thousands):

		Years Ended December 31,
Agreement	Deliverable	2015		2014		2013
Japan	License	$	1,024	$	518	$	566
	Milestones		—		—		12,500
	Total license and milestone revenue	$	1,024	$	518	$	13,066
	Collaboration services revenue*	$	198	$	356	$	433

When and if available compounds, manufacturing — clinical supplies and committee services have each been identified as separate units of accounting with standalone value and amounts allocable to these elements have been recognized and classified within the Collaboration services revenue line item within the consolidated statements of operations.

The total arrangement consideration has been allocated to each of the following deliverables under the Japan Agreement, along with any associated deferred revenue as follows (in thousands):

	Cumulative Revenue Through December 31, 2015		Deferred Revenue at December 31, 2015		Total Consideration Through December 31, 2015
License	$	42,245	$	—	$	42,245
When and if available compounds		14		28		42
Manufacturing--clinical supplies		1,966		—		1,966
Committee services		16		—		16
Total license and collaboration services revenue	$	44,241	$	28	$	44,269

Amounts recognized as revenue under the Europe Agreement were as follows (in thousands):

		Years Ended December 31,
Agreement	Deliverable	2015		2014		2013
Europe	License	$	17,677	$	13,935	$	9,260
	Milestones		—		—		—
	Total license and milestone revenue	$	17,677	$	13,935	$	9,260
	Collaboration services revenue*	$	2,697	$	3,179	$	2,902

When and if available compounds, manufacturing — clinical supplies, development services — in progress at the time of signing of the agreement, and committee services have each been identified as a separate unit of accounting with standalone value and amounts allocable to these units have been recognized in revenue as services are performed and classified within the Collaboration services revenue line item within the consolidated statements of operations.

The total arrangement consideration has been allocated to each of the following deliverables under the Europe Agreement, along with any associated deferred revenue as follows (in thousands):

	Cumulative Revenue Through December 31, 2015		Deferred Revenue at December 31, 2015		Total Consideration Through December 31, 2015
License	$	401,316	$	—	$	401,316
When and if available compounds		332		432		764
Manufacturing--clinical supplies		9,612		—		9,612
Development services--in progress		32,154		—		32,154
Committee services		278		—		278
Total license and collaboration services revenue	$	443,692	$	432	$	444,124

Amounts recognized as revenue under the U.S./RoW and China Agreements were as follows (in thousands):

		Years Ended December 31,
Agreement	Deliverable	2015		2014		2013
U.S. / RoW and China	License	$	114,392	$	102,738	$	72,635
	Milestones		15,000		—		—
	Total license and milestone revenue	$	129,392	$	102,738	$	72,635
	Collaboration services revenue*	$	29,731	$	16,820	$	3,843
	China single unit of accounting**	$	—	$	—	$	—

Co-development, information sharing, and committee services have been combined into a single unit of accounting because the requirements to share information and serve on committees are useful only in combination with the development services, and because all three items are delivered over the same period while manufacturing — clinical supplies has been identified as a separate unit of accounting with standalone value and amounts allocable to this unit of accounting have been recognized and classified within the Collaboration services revenue line item within the consolidated statements of operations.

All revenues attributable to the China unit of accounting are deferred until all deliverables are met. The China license and collaboration services elements have been combined into a single unit of accounting and consideration allocable to this unit is being deferred due to FibroGen’s retention of manufacturing rights and lack of standalone value.

The total arrangement consideration has been allocated to each of the following deliverables under the U.S./RoW and China Agreements, along with any associated deferred revenue as follows (in thousands):

	Cumulative Revenue Through December 31, 2015		Deferred Revenue at December 31, 2015		Total Consideration Through December 31, 2015
License	$	289,766	$	—	$	289,766
Co-development, information sharing & committee services		50,162		37,936		88,098
Manufacturing--clinical supplies		232		70		302
China-single unit of accounting		—		59,394		59,394
Total license and collaboration services revenue	$	340,160	$	97,400	$	437,560

Other Revenues

Other revenues consist of royalty payments received, which are recorded on a monthly basis as they are reported to the company and collagen feasibility sales. Other revenues were immaterial for each of the three years ended December 31, 2015.

Deferred Revenue

Deferred revenue represents amounts billed to the Company’s collaboration partners for which the related revenues have not been recognized because one or more of the revenue recognition criteria have not been met. The current portion of deferred revenue represents the amount to be recognized within one year from the balance sheet date based on the estimated performance period of the underlying deliverables. The long term portion of deferred revenue represents amounts to be recognized after one year through the end of the non-contingent performance period of the underlying deliverables. The long term portion of deferred revenue also includes amounts allocated to the China unit of accounting under the AstraZeneca arrangement as revenue recognition associated with this unit of accounting is tied to the commercial launch of the products within China, which is not expected to occur within the next year.

Fair Value Measurements

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Fair Value Measurements

4.	Fair Value Measurements

In accordance with the authoritative guidance on fair value measurements and disclosures under U.S. GAAP, the Company presents all financial assets and liabilities and any other assets and liabilities that are recognized or disclosed at fair value on a nonrecurring basis. The guidance defines fair value, establishes a framework for measuring fair value in generally accepted accounting principles and expands disclosures about fair-value measurements. The guidance also requires fair value measurements be classified and disclosed in one of the following three categories:

Level 1: Quoted prices in active markets for identical assets or liabilities.

Level 2: Observable inputs other than quoted prices in active markets for identical assets or liabilities.

Level 3: Unobservable inputs.

The Company values certain assets and liabilities, focusing on the inputs used to measure fair value, particularly in instances where the measurement uses significant unobservable (Level 3) inputs. The Company’s financial instruments are valued using quoted prices in active markets (Level 1) or based upon other observable inputs (Level 2). The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and considers factors specific to the asset or liability. In addition, the categories presented do not suggest how prices may be affected by the size of the purchases or sales, particularly with the largest highly liquid financial issuers who are in markets continuously with non-equity instruments, or how any such financial assets may be impacted by other factors such as U.S. government guarantees. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement.

The fair values of the Company’s financial assets that are measured on a recurring basis are as follows (in thousands):

	December 31, 2015
	Level 1		Level 2		Level 3		Total
Corporate bonds	$	—	$	126,103	$	—	$	126,103
Bond and mutual funds		25,052		—		—		25,052
Equity investments		197		—		—		197
Money market funds		77,639		—		—		77,639
Certificate of deposits		—		8,215		—		8,215
Total	$	102,888	$	134,318	$	—	$	237,206

	December 31, 2014
	Level 1		Level 2		Level 3		Total
Corporate bonds	$	—	$	158,432	$	—	$	158,432
Equity investments		201		—		—		201
Money market funds		13,802		—		—		13,802
Total	$	14,003	$	158,432	$	—	$	172,435

The Company’s Level 2 investments are valued using third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar investments, issuer credit spreads, benchmark investments, prepayment/default projections based on historical data and other observable inputs.

The fair values of the Company’s financial liabilities that are carried at historical cost are as follows (in thousands):

	December 31, 2015
	Level 1		Level 2		Level 3		Total
Lease financing obligations	$	—	$	—	$	97,445	$	97,445

	December 31, 2014
	Level 1		Level 2		Level 3		Total
Cease-use liability	$	—	$	—	$	184	$	184
Lease financing obligations		—		—		97,221		97,221
Total	$	—	$	—	$	97,405	$	97,405

The fair value of the Company’s financial liabilities were each derived by using an income approach which required Level 3 inputs such as discounted estimated future cash flows.

There were no transfers of assets or liabilities between levels for the years ended December 31, 2015, 2014 or 2013.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Balance Sheet Components

12 Months Ended

Dec. 31, 2015

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Components

5.	Balance Sheet Components

Cash and Cash Equivalents

Cash and cash equivalents consisted of the following (in thousands):

	December 31,
	2015		2014
Cash	$	75,685	$	151,653
Money market funds		77,639		13,802
Total cash and cash equivalents	$	153,324	$	165,455

Property and Equipment

Property and equipment consisted of the following (in thousands):

	December 31,
	2015			2014
Laboratory equipment	$	18,233		$	17,114
Computer equipment		5,701			5,106
Furniture and fixtures		5,361			5,082
Leasehold improvements		93,380			92,790
Building shell (Refer to Note 8)		53,879			53,879
Construction in progress		193			519
Total property and equipment	$	176,747		$	174,490
Less: accumulated depreciation		(47,727	)		(42,319	)
Property and equipment, net	$	129,020		$	132,171

Depreciation expense for the years ended December 31, 2015, 2014 and 2013 was $5.7 million, $4.5 million, and $5.1 million, respectively.

Investments

All investments are classified as available-for-sale. The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s available-for-sale investments by major investments type are summarized in the tables below (in thousands):

	December 31, 2015
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Corporate bonds	$	126,522	$	54	$	(473	)	$	126,103
Certificate of deposits		8,217		—		(2	)		8,215
Bond and mutual funds		25,052		—		—			25,052
Equity investments		126		71		—			197
Total investments	$	159,917	$	125	$	(475	)	$	159,567

	December 31, 2014
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Corporate bonds	$	158,692	$	254	$	(514	)	$	158,432
Equity investments		124		77		—			201
Total investments	$	158,816	$	331	$	(514	)	$	158,633

The contractual maturities of available-for-sale investments were as follows (in thousands):

	December 31,
	2015
Within one year	$	12,797
After one year through four years		121,521
Total debt investments		134,318
Bond and mutual funds		25,052
Equity investments		197
Total investments		159,567

Available-for-sale investments are reported at fair value and as such, their associated unrealized gains and losses are reported as a separate component of stockholders’ equity within accumulated other comprehensive income (loss).

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	December 31,
	2015		2014
Preclinical and clinical trial accruals	$	27,973	$	25,418
Payroll and related accruals		13,535		15,608
Professional services		1,662		2,401
Other		4,762		5,558
Total accrued liabilities	$	47,932	$	48,985

Product Development Obligations

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Product Development Obligations

6.	Product Development Obligations

The Technology Development Center of the Republic of Finland (“TEKES”) product development obligations consist of 11 separate advances (each in the form of a note agreement) received by FibroGen Europe between 1996 and 2008 from TEKES. These advances are granted on a project by project basis to fund various product development efforts undertaken by FibroGen Europe only. Each separate note bears interest (not compounded) calculated as one percentage point less than the Bank of Finland rate in effect at the time of the note, but no less than 3.0%.

If the research work funded by TEKES does not result in an economically profitable business or does not meet its technological objectives, TEKES may, on application from FibroGen Europe, forgive each of these loans, including accrued interest, either in full or in part. As of December 31, 2015 and 2014, the Company had $10.3 million and $11.5 million of principal outstanding, respectively, and $4.8 million and $5.0 million of interest accrued, respectively, which were presented in the product development obligations line on the consolidated balance sheets.

The Company is not a guarantor of these loans, and these loans are not repayable by FibroGen Europe until it has distributable funds.

Convertible Note Payable

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Convertible Note Payable

7.	Convertible Note Payable

In January 2013, FibroGen China entered into a $0.6 million convertible promissory note. The note bears simple interest at a rate of two percent (2.00%) per annum, accrued on an annual basis in arrears. The outstanding principal balance and unpaid accrued interest on the note is due and payable upon the earlier of (a) the effectiveness of the initial public offering of FibroGen China or (b) the eight year anniversary of the date of the note. The total outstanding principal balance and unpaid accrued interest on the note will be converted into Series A Preferred Stock of FibroGen China at the option of the lender or by the Company at its discretion.

Commitment and Contingencies

12 Months Ended

Dec. 31, 2015

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

8	Commitments and Contingencies

Operating Leases

Future minimum lease payments under all non-cancelable operating lease obligations as of December 31, 2015 are as follows (in thousands):

Year Ending	Operating Leases
2016	$	128
2017		84
Total minimum payments	$	212

Facility Lease Financing Obligations

FibroGen, Inc.

In September 2006, the Company entered into a long-term property lease with Shorenstein Properties LLC (“Alexandria” or “landlord”) providing the Company with 234,249 square feet of space for an initial term of 15 years. Upon signing, a stand-by letter of credit was established in the amount of $7.3 million which has been included in restricted cash. The agreement included an expansion option to occupy part of an adjacent building within 31 months of the lease commencement date of November 20, 2008. In June 2012, the Company gave notice to its landlord that it would not exercise this expansion option, which resulted in a $5.0 million payment liability to the landlord which is being financed over the remaining lease term of its lease.

In connection with this lease, the Company was responsible for approximately 60% of the construction costs for the tenant improvements. The Company is deemed, for accounting purposes only, to be the accounting owner of the entire project including the building shell, even though it is not the legal owner. The balance of the tenant improvements were paid by Alexandria in the form of a tenant improvement allowance of $140.50 per square foot of rentable space, or $32.5 million.

In connection with the Company’s accounting for this transaction, the Company capitalized Alexandria’s costs of constructing the building shell which totaled $50.8 million, and recognized a corresponding lease financing obligation. The Company also recognized, as an additional lease financing obligation, the reimbursements totaling $32.5 million from landlord for tenant improvements since these reimbursements are also deemed to be a financing obligation.

A portion of the monthly lease payment will be allocated to land rent and recorded as an operating lease expense and the non-interest portion of the amortized lease payments to the landlord related to rent of the building will be applied to the lease financing liability.

In addition, the Company had a leased facility located in South San Francisco, California, which was used as its corporate headquarters prior to moving to its current facility in 2008. The South San Francisco facility is approximately 106,000 square feet and was fully subleased. This lease and associated subleases terminated in February 2015.

FibroGen China

In February 2013, the Company entered into a long-term property lease with Beijing Economic-Technological Development Area (“BDA”) Management Committee for a pilot plant located in Beijing Yizhuang Biomedical Park (“BYBP”) of BDA. The leased space is 4,820 square meters over an eight (8) year term starting February 1, 2013.

In connection with this lease, the Company was responsible for approximately 100% of the construction costs for the tenant improvements. The Company is deemed, for accounting purposes only, to be the accounting owner of the entire project, including the building shell, even though it is not the legal owner.

In connection with the Company’s accounting for this transaction, the Company capitalized BDA Management Committee’s costs of constructing the building shell which totaled $3.1 million, and recognized a corresponding lease financing obligation. The Company also recognized, as an additional lease financing obligation, the reimbursements totaling $0.5 million from BYBP for a rent subsidy since this reimbursement is also deemed to be a financing obligation.

Future minimum lease payments, on a consolidated basis, under the Company’s facility lease financing obligations as of December 31, 2015 are as follows (in thousands):

Year Ending	Lease financing obligations
2016	$	13,699
2017		14,030
2018		14,252
2019		14,468
2020		14,689
Thereafter		41,378
Total minimum payments	$	112,516

Apart from the property leases with Alexandria and BDA Management Committee, rent expense for leased facilities under operating lease commitments was $2.7 million, $2.9 million, and $3.0 million for the years ended December 31, 2015, 2014 and 2013, respectively. The Company received sublease income of $3.4 million, $5.0 million, and $4.5 million for the years ended December 31, 2015, 2014 and 2013, respectively.

Indemnification Agreements

The Company enters into standard indemnification arrangements in the ordinary course of business, including for example, service, manufacturing and collaboration agreements. Pursuant to these arrangements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified parties for losses suffered or incurred by the indemnified party, including in connection with intellectual property infringement claims by any third party with respect to its technology. The term of these indemnification agreements is generally perpetual any time after the execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these arrangements is not determinable. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements. As a result, the Company believes the estimated fair value of these arrangements is minimal.

The Company has entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the extent permissible under applicable law.

Redeemable Convertible Preferred Stock and Equity (Deficit)

12 Months Ended

Dec. 31, 2015

Redeemable Convertible Preferred Stock And Equity Deficit [Abstract]

Redeemable Convertible Preferred Stock and Equity (Deficit)

9.	Redeemable Convertible Preferred Stock and Equity (Deficit)

Convertible Preferred Stock (“Preferred Stock”)

As of December 31, 2013 and immediately prior to the initial public offering, the Company had authorized 125,000,000 shares of Preferred Stock. All shares of Preferred Stock had a par value of $0.01 per share.

Upon the closing of the IPO, all outstanding shares of the Company’s convertible preferred stock automatically converted into 33,919,954 shares of common stock. As of December 31, 2015 and 2014, there was no outstanding convertible preferred stock.

Subsidiary Stock and Non-Controlling Interests

FibroGen Europe

As of December 31, 2015 and 2014, respectively, FibroGen Europe had a total of 42,619,022 shares of Preferred Stock outstanding, of which there were 1,700,845 shares of Series A Preferred Stock, 1,875,000 shares of Series B Preferred Stock, 1,599,503 shares of Series C Preferred Stock, 1,520,141 shares of Series D Preferred Stock, 459,565 shares of Series E Preferred Stock, 5,714,332 shares of Series F Preferred Stock, 9,927,500 shares of Series G Preferred Stock and 19,822,136 shares of Series H Preferred Stock, all of which shares no longer have any right to be exchanged for FibroGen, Inc. Common Stock.

The holders of FibroGen Europe’s shares of Preferred Stock (“Preferred Shares”) have the following rights, preferences and privileges:

Dividend Rights — When the assets of FibroGen Europe are distributed (except for distribution in a liquidation), Preferred Shares shall have the same rights to dividend or other forms of distribution as shares of Common Stock of FibroGen Europe. In the event of a merger, holders of Preferred Shares do not have the right to demand FibroGen Europe to redeem all or part of their Preferred Shares. FibroGen Europe may repurchase shares of Common Stock or Preferred Shares for consideration.

Pre-emptive Right — Preferred Shares shall have pre-emptive subscription right in accordance with the Finnish Limited Liability Companies Act if additional shares are issued, option rights are given, or convertible loan is taken, provided, however, that the foregoing pre-emptive right does not apply to a directed share issue, for which two thirds (2/3) of the voting shares represented at a general meeting of shareholders approve for an important legitimate cause.

Redemption Right — If a Preferred Share can be redeemed by a majority shareholder owning more than ninety percent (90%) of the shares of FibroGen Europe in accordance with the provisions of the Finnish Limited Liability Companies Act, the minority holders of Preferred Shares have the right to request redemption of their shares.

Voting Right — Each share has one vote. Preferred Shares have voting rights only in situations that are specifically provided in the Articles of Association, which include a merger transaction and directed share issue. In addition, Preferred Shares have right to vote in a general shareholder meeting for amending the Articles of Association if the amendment will affect the rights of Preferred Shares.

Conversion Right (1-for-1 basis into Common Stock of FibroGen Europe):

Voluntary conversion right: Preferred Shares can be converted into common shares upon the written request of a shareholder provided that the conversion is feasible within the maximum and minimum amounts of shares of classes of FibroGen Europe as set forth in its Articles of Association. Such request can be withdrawn before the notification of conversion is filed with the Finnish Trade Register.

Compulsory conversion right: Preferred Shares will be converted into common shares if (i) FibroGen Europe’s shares are listed in a stock exchange or other trading system in the European Economic Area, or (ii) FibroGen Europe’s recombinant collagen and gelatin production technology is being put into commercial use in the area of EU and certain other European states. Commercial use means there is income generated from the first commercial sale of the products incorporating the above mentioned technology and does not include license fees, development financing, milestone payments or income from test products or equipment used in research. The board of directors of FibroGen Europe shall notify the shareholders of the compulsory conversion in writing, and the shareholders shall request to convert their shares within the timeframe provided in the notification. Should the shareholders fail to make the conversion request within the time limit, FibroGen Europe may redeem the shares of such shareholders.

Liquidation Right — In the event of a dissolution of FibroGen Europe, holders of Preferred Shares are entitled to be paid in an amount equal to the subscription price of the shares before any distribution is made to holders of common shares. Among holders of Preferred Shares, holders of shares of Series F Preferred Stock are entitled to be paid in an amount equal to the subscription price of Series F Preferred Stock before any distribution is made to holders of other Preferred Shares.

FibroGen China

FibroGen China had 6,758,000 Series A Preference Shares outstanding as of December 31, 2015 and 2014, respectively. The holders of the FibroGen China Series A Preference Shares have the following rights, preferences and privileges:

Liquidation — In the event of liquidation, dissolution, or winding up of the Company, either voluntary or involuntary, including by means of a merger, the holders of FibroGen China Series A Preference Shares are entitled to be paid an amount equal to the product of the number of shares held by a holder of shares of FibroGen China Series A Preference Shares and the original issue price of $1.00 (subject to equitable adjustment for any stock dividend, combination, split, reclassification, recapitalization) plus all declared and unpaid dividends thereon.

Conversion — Each share of FibroGen China Series A Preference Shares is convertible into the number of fully paid and non-assessable shares of Common Stock of FibroGen China that results from dividing the original issue price by the conversion price in effect at the time of the conversion, subject to adjustments for stock splits, stock dividends, reclassifications and like events. The FibroGen China Series A Preference Shares have a conversion price that is equal to the original issuance price such that the conversion ratio to FibroGen China Common Stock is 1:1 as of all periods presented.

Voting — The holders of FibroGen China Series A Preference Shares are entitled to vote together with the FibroGen China Common Stock holders on all matters submitted for a vote of the stockholders. The holder of each share of FibroGen China Series A Preference Shares has the number of votes equal to the number of shares of FibroGen China Common Stock into which it is convertible.

Dividends — The holders of FibroGen China Series A Preference Shares are entitled to receive cash dividends when and if declared, at a rate of 6%.

Non-Controlling Interests

Non-controlling interest positions related to the issuance of subsidiary stock as described above are reported as a separate component of consolidated equity from the equity attributable to the Company’s stockholders at December 31, 2015 and 2014. In addition, the Company does not allocate losses to the non-controlling interests as the outstanding shares representing the non-controlling interest do not represent a residual equity interest in the subsidiary. Upon the initial public offering and as described above, all eligible FibroGen Europe preferred shares were exchanged for 958,996 shares of FibroGen Common Stock. No other FibroGen Europe shares have the right to be exchanged for FibroGen, Inc. Common Stock.

Common Stock

Each share of Common Stock is entitled to one vote. The holders of Common Stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors, subject to the prior rights of holders of all classes of stock outstanding.

Shares of Common Stock outstanding, shares of stock plans outstanding and shares reserved for future issuance related to stock options and RSUs grant and Employee Stock Purchase Plan (“ESPP”) purchases are as follows (in thousands):

	December 31,
	2015		2014
Common stock outstanding		61,985		59,046
Stock options outstanding		13,583		14,427
RSUs outstanding		865		560
Common stock warrants outstanding		7		173
Shares reserved for future stock options and RSUs grant		3,394		5,358
Shares reserved for future ESPP offering		1,285		1,600
Total shares of common stock reserved		81,119		81,164

Stock Plans

Stock Option and RSU Plans

Under the Company’s Amended and Restated 2005 Stock Plan (“2015 Stock Plan”), the Company may issue shares of Common Stock and options to purchase Common Stock and other forms of equity incentives to employees, directors and consultants. Options granted under the 2005 Stock Plan may be incentive stock options or nonqualified stock options. Incentive stock options (“ISO”) may be granted only to employees and officers of the Company. Nonqualified stock options (“NSO”) and stock purchase rights may be granted to employees, directors and consultants. The board of directors has the authority to determine to whom options will be granted, the number of options, the term and the exercise price. Options are to be granted at an exercise price not less than fair market value for an ISO or an NSO. Options generally vest over four years. Options expire no more than 10 years after date of grant. Upon the effective date of the registration statement related to the Company’s initial public offering, the 2005 Plan was amended to cease the grant of any additional awards thereunder, although the Company will continue to issue common stock upon the exercise of previously granted stock options under the 2005 Plan.

In September 2014, the Company adopted a 2014 Equity Incentive Plan (the “2014 Plan”) which became effective on November 13, 2014. The 2014 Plan is the successor equity compensation plan to the 2005 Plan. The 2014 Plan will terminate on November 12, 2024. The 2014 Plan provides for the grant of incentive stock options, nonqualified stock options, restricted stock awards, stock appreciation rights, performance stock awards, performance cash awards, restricted stock units and other stock awards to employees, directors and consultants. Stock options granted must be at prices not less than 100% of the fair market value at date of grant. Option vesting schedules are determined by the Company at the time of issuance and generally have a four year vesting schedule (25% vesting on the first anniversary of the vesting base date and quarterly thereafter over the next 3 years). Options generally expire ten years from the date of grant unless the optionee is a 10% stockholder, in which case the term will be five years from the date of grant. Unvested options exercised are subject to the Company’s repurchase right. As of December 31, 2015, the Company has reserved 3,393,948 shares of its common stock for issuance under the 2014 Plan, and shares reserved for issuance will increase January 1 of each year commencing on January 1, 2016 and ending on January 1, 2024 by the lesser of (i) the amount equal to 4% of the number of shares issued and outstanding on December 31 immediately prior to the date of increase or (ii) such lower number of shares as may be determined by the board of directors.

Issuance of shares upon share option exercise or share unit conversion is made through issuance of new shares authorized under the plan.

Certain Common Stock option holders have the right to exercise unvested options, subject to a right held by the Company to repurchase the stock, at the original exercise price, in the event of voluntary or involuntary termination of employment of the stockholder. The shares are generally released from repurchase provisions ratably over four years. The Company accounts for the cash received in consideration for the early exercised options as a liability. At December 31, 2015 and 2014, no shares of Common Stock were subject to repurchase by the Company.

Stock option transactions, including forfeited options granted under the 2014 Plan as well as prior plans, are summarized below:

	Shares (In thousands)			Weighted Average Exercise per Share		Weighted Average Remaining Contractual Life (In Years)		Aggregate Intrinsic Value (In thousands)
Outstanding at December 31, 2014		14,427		$	7.10
Granted		1,891			27.27
Exercised		(2,362	)		4.28
Expired		(29	)		3.68
Forfeited		(344	)		18.08
Outstanding at December 31, 2015		13,583			10.12		6.07	$	276,401
Vested and expected to vest, December 31, 2015		13,321			9.84		6.01		274,820
Exercisable at December 31, 2015		10,029		$	6.13		5.11	$	244,134

The total intrinsic value of options exercised during the years ended December 31, 2015, 2014, and 2013 was $48.7 million, $6.5 million, and $0.3 million, respectively.

The following table summarizes restricted stock unit activity:

	Number of Shares			Fair Value at Grant
Unvested at December 31, 2014		559,582		$	18.00
Granted		586,008			29.66
Vested		(241,497	)		18.00
Forfeited		(39,244	)		25.08
Unvested at December 31, 2015		864,849		$	25.58

The estimated weighted-average fair value of the awards granted during the years ended December 31, 2015 and 2014 was $29.66 and $18.00, respectively. The Company did not grant any RSUs prior to January 1, 2014. There were no RSUs that were settled or exercised during the year ended December 31, 2015.

ESPP

In September 2014, the Company adopted a 2014 Employee Stock Purchase Plan (the “2014 Purchase Plan”) which became effective on November 13, 2014. The 2014 Purchase Plan is designed to enable eligible employees to periodically purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan or IRS limitations ($25,000.00 for 2015). At the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last day of the offering period. Purchases are accomplished through participation in discrete offering periods. The 2014 Purchase Plan is intended to qualify as an ESPP under Section 423 of the Internal Revenue Code. The Company has reserved 1,600,000 shares of its common stock for issuance under the 2014 Purchase Plan and shares reserved for issuance will increase January 1 of each year commencing January 1, 2016 by the lesser of (i) a number of shares equal to 1% of the total number of outstanding shares of common stock on December 31 immediately prior to the date of increase; (ii) 1,200,000 shares or (iii) such number of shares as may be determined by the board of directors. There were no shares purchased by employees under the 2014 Purchase Plan for the year ended December 31, 2014. There were 315,385 shares purchased by employees under the 2014 Purchased Plan for the year ended December 31, 2015.

The expected term of 2014 Purchase Plan shares is the average of the remaining purchase periods under each offering period.

Stock-Based Compensation

Stock-based compensation related to options granted is allocated to research and development and general and administrative expense for the years ended December 31, 2015, 2014, and 2013 was as follows (in thousands):

	Years Ended December 31,
	2015		2014		2013
Research and development	$	16,987	$	10,893	$	1,925
General and administrative		10,694		7,805		1,519
Total stock-based compensation expense	$	27,681	$	18,698	$	3,444

The Company estimates the fair value of stock options using the Black-Scholes option valuation model. The fair value of employee stock options is being amortized on a straight-line basis over the requisite service period of the awards.

The Company, in making its determinations of the fair value of its Common Stock, considered a variety of quantitative and qualitative factors, including (i) net present value of the Company’s projected earnings, (ii) fair market value of the stock of comparable publicly-traded companies, (iii) any third party transactions involving the Company’s convertible preferred stock, (iv) liquidation preferences of the Company’s preferred stock and the likelihood of conversion of the preferred stock, (v) changes in the Company’s business operations, financial condition and results of operations over time, including cash balances and burn-rate, (vi) the status of new product development, and (vii) general financial market conditions. Subsequent to the IPO, the fair market value of common stock is based on the closing price of the Company’s common stock as reported on the NASDAQ Global Select Market on the date of the grant.

The fair value of employee stock options was estimated using the following assumptions:

Expected Term. Expressed as a weighted-average, the expected life of the options is based on the average period the stock options are expected to be outstanding and was based on the Company’s historical information of the option exercise patterns and post-vesting termination behavior as well as contractual terms of the instruments.

Expected Volatility. Since the Company has very little historical data regarding the volatility of its Common Stock, the expected volatility is based upon the historical volatility of comparable public entities. In evaluating comparable companies, the Company considered factors such as industry, stage of life cycle, size and duration as a public company.

Risk-Free Interest Rate. Expressed as a weighted-average, the risk-free interest rate assumption is based on the U.S. Treasury instruments whose term was consistent with the expected term of the Company’s stock options.

Expected Dividend Yield. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future.

The assumptions used to estimate the fair value of stock options granted and ESPPs using the Black-Scholes option valuation model were as follows:

	Years Ended December 31,
	2015			2014			2013
Stock Options
Expected term (in years)		5.2			5.1			4.1
Expected volatility		69.9	%		62.8	%		71.6	%
Risk-free interest rate		1.7	%		1.7	%		0.8	%
Expected dividend yield		—			—			—
Weighted average estimated fair value	$	16.12		$	9.51		$	6.19

ESPPs
Expected term (in years)	1.1 - 1.3				1.2			—
Expected volatility	64.8 - 65.3%			61.7 - 65.5%				—	%
Risk-free interest rate		0.3	%	0.1 - 0.4%				—	%
Expected dividend yield		—			—			—
Weighted average estimated fair value	$	10.54		$	13.22		$	—

As of December 31, 2015, there was $34.1 million of total unrecognized compensation costs, net of estimated forfeitures, related to non-vested stock option awards granted that will be recognized on a straight-line basis over the weighted-average period of 2.32 years. As of December 31, 2015, there was $16.2 million of total unrecognized compensation costs, net of estimated forfeitures, related to non-vested RSUs granted that will be recognized on a straight-line basis over the weighted-average period of 2.81 years.

Warrants

The following warrants to purchase shares of Common Stock were issued in connection with certain facility and equipment lease financing arrangements and are outstanding at December 31, 2015:

Year of Issuance	Number of Shares		Exercise Price per Share		Reason for Issuance	Expiration Date
1996		1,600	$	4.38	Issued in connection with lease agreement	Five years after initial public offering or upon merger or sale of the Company’s assets, whichever occurs first
2000		5,538	$	15.00	Issued in connection with lease agreement	Five years after initial public offering or upon merger or sale of the Company’s assets, whichever occurs first
		7,138

Net Loss Per Share

12 Months Ended

Dec. 31, 2015

Earnings Per Share [Abstract]

Net Loss Per Share

10.	Net Loss Per Share

The Company applies the two-class method to calculate basic and diluted net loss per share of Common Stock. The Junior Preferred Stock are participating securities due to their dividend rights and the Senior Preferred Stock has stated dividend rates. The two-class method is an earnings allocation method under which earnings per share is calculated for Common Stock considering a participating security’s rights to undistributed earnings as if all such earnings had been distributed during the period. The Company’s participating securities are not included in the computation of net loss per share in periods of net loss because the preferred stockholders have no contractual obligation to participate in losses.

The following securities were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented (in thousands):

	Years Ended December 31,
	2015		2014		2013
Senior Preferred Stock		—		—		15,336
Junior Preferred Stock		—		—		18,584
Employee stock options		13,583		14,427		11,084
RSUs outstanding		865		560		—
Warrants		7		173		173
FibroGen Europe Preferred stock		—		—		959
		14,455		15,160		46,136

FibroGen, Inc. 401(k) Plan

12 Months Ended

Dec. 31, 2015

Compensation And Retirement Disclosure [Abstract]

FibroGen, Inc. 401(k) Plan

11	FibroGen, Inc. 401(k) Plan

Substantially all of the Company’s full-time United States of America-based employees are eligible to make contributions to the Company’s 401(k) Plan. Under this plan, participating employees may defer up to 60% of their pretax salary during the year, but not more than statutory limits. The Company may elect to match employee contributions; no such matching contributions were made for the year ended December 31, 2013. Matching contributions of $2.5 million and $1.9 million were made during year ended December 31, 2015 and 2014, respectively.

Income Taxes

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Income Taxes

12.	Income Taxes

The components of loss before income taxes are as follows (in thousands):

	Years Ended December 31,
	2015			2014			2013
Domestic	$	(66,411	)	$	(46,998	)	$	(3,107	)
Foreign		(19,126	)		(12,506	)		(11,836	)
Loss before provision for income taxes	$	(85,537	)	$	(59,504	)	$	(14,943	)

The provision for income taxes consists of the following (in thousands):

	Years Ended December 31,
	2015		2014		2013
Current:
Federal	$	—	$	—	$	—
State		2		—		—
Foreign		240		—		—
Total current	$	242	$	—	$	—
Deferred:
Federal	$	—	$	—	$	—
State		—		—		—
Foreign		—		—		—
Total deferred	$	—	$	—	$	—
Total provision from income taxes	$	242	$	—	$	—

The following is the reconciliation between the statutory federal income tax rate and the Company’s effective tax rate:

	Years Ended December 31,
	2015			2014			2013
Tax at statutory federal rate		34.0	%		34.0	%		34.0	%
State tax		—	%		—	%		—	%
Stock-based compensation expense		(4.6	)%		(4.6	)%		(5.7	)%
Net operating losses not benefitted		(21.7	)%		(22.4	)%		(1.6	)%
Foreign net operating losses benefitted		(7.6	)%		(7.1	)%		(26.9	)%
Other		(0.4	)%		0.1	%		0.2	%
Total		(0.3	)%		—	%		—	%

Significant components of the Company’s deferred tax assets are as follows (in thousands):

	December 31,
	2015			2014
Federal and state net operating loss carryforwards	$	53,393		$	44,748
Tax credit carryforwards		26,620			24,395
Foreign net operating loss carryforwards		8,421			6,485
Stock-based compensation		8,512			5,836
Lease obligations		4,335			5,204
Reserves and accruals		4,891			5,075
Deferred revenue		10,484			3,304
Other		915			950
Subtotal		117,571			95,997
Less: Valuation allowance		(116,718	)		(94,731	)
Net deferred tax assets		853			1,266

Fixed assets		(853	)		(1,266	)
Net deferred tax liabilities		(853	)		(1,266	)
Total net deferred tax assets	$	—		$	—

A valuation allowance has been provided to reduce the deferred tax assets to an amount management believes is more likely than not to be realized. Expected realization of the deferred tax assets for which a valuation allowance has not been recognized is based on upon the reversal of existing temporary differences and future taxable income.

The valuation allowance increased by $22.0 million, $21.6 million and $2.2 million for the years ended December 31, 2015, 2014 and 2013, respectively. Due to uncertainty surrounding the realization of the favorable tax attributes in the future tax returns, the Company has established a valuation allowance against its otherwise recognizable net deferred tax assets.

At December 31, 2015, the Company had net operating loss carryforwards available to offset future taxable income of approximately $185.1 million and $270.1 million for federal and state tax purposes, respectively. These carryforwards will begin to expire in 2026 for federal and 2018 for state purposes, if not utilized before these dates. The Company also had foreign net operating loss carryforwards of approximately $35.6 million which expire between 2016 and 2025 if not utilized.

At December 31, 2015, the Company had approximately $27.0 million of federal and $15.6 million of California research and development tax credit and other tax credit carryforwards available to offset future taxable income. The federal credits begin to expire in 2018 and the California research credits have no expiration dates.

The Company tracks a portion of its deferred tax assets attributable to stock option benefits in a separate memorandum account. Therefore, these amounts are not included in the Company’s gross or net deferred tax assets. The benefit of these stock options will not be recorded in equity unless it reduces taxes payable. As of December 31, 2015, the impact related to stock option benefits was approximately $15.8 million.

Federal and state tax laws impose substantial restrictions on the utilization of net operating loss and credit carryforwards in the event of an “ownership change” for tax purposes, as defined in IRC Section 382. The Company reviewed its stock ownership for year ended December 31, 2015 and concluded no ownership changes occurred which would result in a reduction of its net operating loss or in its research and development credits expiring unused. If additional ownership change occurs, the utilization of net operating loss and credit carryforwards could be significantly reduced.

Uncertain Tax Positions

The Company had unrecognized tax benefits of approximately $24.2 million as of December 31, 2015. These unrecognized tax benefits, if recognized, would not affect the effective tax rate. The interest accrued as of December 31, 2015 was immaterial. There were no interest or penalties accrued as of December 31, 2014.

A reconciliation of the beginning and ending amounts of unrecognized income tax benefits during the years ended December 31, 2013, 2014 and 2015 is as follows (in thousands):

	Federal and State
Balance as of January 1, 2013	$	12,545
Increase due to prior positions		294
Increase due to current year position		680
Balance as of December 31, 2013		13,519
Increase due to prior positions		1,493
Increase due to current year position		4,110
Balance as of December 31, 2014		19,122
Decrease due to prior positions		(2,382	)
Increase due to current year position		7,473
Balance as of December 31, 2015	$	24,213

Unrecognized tax benefits may change during the next twelve months for items that arise in the ordinary course of business. The Company does not anticipate a material change to its unrecognized tax benefits over the next twelve months that would affect the Company’s effective tax rate.

The Company classifies interest and penalties as a component of tax expense, if any.

The Company files income tax returns in the U.S. federal jurisdiction, U.S. state and other foreign jurisdictions. The U.S. federal and U.S. state taxing authorities may choose to audit tax returns for tax years beyond the statute of limitation period due to significant tax attribute carryforwards from prior years, making adjustments only to carryforward attributes. The foreign statute of limitation generally remains open from 2006 to 2015. The Company is not currently under audit in any tax jurisdiction.

Related Party Transactions

12 Months Ended

Dec. 31, 2015

Related Party Transactions

13.	Related Party Transactions

Astellas is an equity investor in the Company and considered a related party. During the years ended December 31, 2015, 2014 and 2013, the Company recorded revenue related to collaboration agreements with Astellas of $21.6 million, $18.0 million, and $25.7 million, respectively. During the years ended December 31, 2015, 2014 and 2013, the Company recorded expense related to collaboration agreements with Astellas of $9.8 million, $11.4 million and $4.0 million, respectively.

As of December 31, 2015 and 2014, accounts receivable from Astellas were $4.5 million and $5.0 million, respectively, and amounts due to Astellas were $2.0 million and $4.3 million, as of the same periods. The amounts due are included in Accrued liabilities on the consolidated balance sheets.

Julian N. Stern, a director of the Company since November 1996, is of counsel to the law firm of Goodwin Procter LLP, which he joined in 2008. He has received, and continues to receive, no compensation from Goodwin Procter LLP since joining it as of counsel. The Company retains Goodwin Procter LLP as legal counsel for various matters, primarily consisting of intellectual property matters. During the years ended December 31, 2015 and 2014, the Company made payments to Goodwin Procter LLP of $0.4 million and less than $0.1 million, respectively. As of December 31, 2014, approximately $0.3 million was included in accrued liabilities in the consolidated balance sheet for amounts due to Goodwin Procter LLP. As of December 31, 2015, the balance of accrued liability for Goodwin Procter LLP was immaterial.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

Segment and Geographic Information

12 Months Ended

Dec. 31, 2015

Segment Reporting [Abstract]

Segment and Geographic Information

14.	Segment and Geographic Information

The Company has determined that the chief executive officer is the chief operating decision maker (“CODM”). The CODM reviews financial information presented for the Company’s various clinical trial programs as well as results on a consolidated basis. License, milestone and collaboration services revenues received are not allocated to various programs for purposes of determining a profit measure and resource allocation decisions are made by the CODM based primarily on consolidated results. As such, the Company has concluded that it operates as one segment. Supplemental enterprise-wide information has been presented below.

Geographic Revenues

Geographic revenues, which are based on the bill to region, are as follows (in thousands):

	Years Ended December 31,
	2015		2014		2013
Europe	$	159,123	$	119,559	$	76,478
Japan (related party)		21,596		17,987		25,661
All other		109		55		31
Total revenue	$	180,828	$	137,601	$	102,170

Geographic Long-Lived Assets

Property and equipment, net by geographic location are as follows (in thousands):

	December 31,
	2015		2014
United States	$	113,628	$	116,099
China		15,392		16,072
Total property and equipment	$	129,020	$	132,171

Customer Concentration

Substantially all of the Company’s revenues to date have been generated from the following collaboration partners that respectively accounted for more than 10% of the Company’s total revenue and accounts receivable:

	As of or for the Year Ended December 31,
	Percentage of Revenue									Percentage of Accounts Receivable
	2015			2014			2013			2015			2014
Astellas—Related party		12	%		13	%		25	%		29	%		37	%
AstraZeneca		88	%		87	%		75	%		71	%		63	%

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=51669610&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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+ Details

Schedule II - Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2015

Valuation And Qualifying Accounts [Abstract]

Schedule II - Valuation and Qualifying Accounts

Schedule II: Valuation and Qualifying Accounts

(in thousands)

			Charged
	Balance at		(Credited)
	Beginning of		to Statement		Deductions,		Balance at
	Year		of Operation		Net		End of Year
Valuation allowances for deferred tax assets
Year ended December 31, 2015	$	94,731	$	21,987	$	—	$	116,718
Year ended December 31, 2014	$	73,144	$	21,587	$	—	$	94,731
Year ended December 31, 2013	$	70,955	$	2,189	$	—	$	73,144

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Basis of Presentation and Liquidity

Foreign Currency Translation

Use of Estimates

Concentration of Credit Risk and Other Risks and Uncertainties

	As of December 31,
	2015			2014
Astellas Pharma Inc. (“Astellas”)—Related party		29	%		37	%
AstraZeneca AB (“AstraZeneca”)		71	%		63	%

Cash, Cash Equivalents and Restricted Cash

Investments

Fair Value of Financial Instruments

Property and Equipment

Impairment of Long-Lived Assets

Revenue Recognition

Substantially all of the Company’s revenues to date have been generated from its collaboration agreements.

·	provides guidance on how deliverables in an arrangement should be separated and how the arrangement consideration should be allocated to the separate units of accounting;

·	requires an entity to determine the selling price of a separate deliverable using a hierarchy of (i) vendor-specific objective evidence (“VSOE”), (ii) third-party evidence (“TPE”), or (iii) best estimate of selling price (“BESP”); and

·	requires the allocation of the arrangement consideration, at the inception of the arrangement, to the separate units of accounting based on relative selling price.

Research and Development Expenses

Clinical Trial Accruals

General and Administrative Expenses

Income Taxes

The Company includes interest and penalties related to unrecognized tax benefits within income tax expense in the Consolidated Statements of Operations.

Stock-Based Compensation

Comprehensive Income (Loss)

Recently Issued and Adopted Accounting Guidance

Recently Issued Accounting Guidance Not Yet Adopted

Description of Operations and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Collaboration Arrangements

Accounting for the Astellas Agreements

For each of the Astellas agreements, the Company has evaluated the deliverables within the respective arrangements and has separated them into various units of accounting.

The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows:

·	Committee service. This deliverable is satisfied and revenue is recognized throughout the course of the various agreements as meetings are attended.

Accounting for the AstraZeneca Agreements

U.S./RoW Agreement:

The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows:

Manufacturing of clinical supplies of products. This deliverable is satisfied as supplies for clinical product are delivered for use in the Company’s clinical trial programs during the development period, or pre-commercialization period. Revenue is recognized based on the estimated proportion of the development services performed during the development period. These estimates are made at the beginning of each accounting period and will likely change throughout the course of the agreements. As new information related to these estimates becomes available, the Company may adjust the timing of revenue recognition related to this unit of accounting.

·	Committee service. This deliverable is satisfied and revenue is recognized throughout the course of the various agreements as meetings are attended.

China Agreement:

The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows:

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Schedule of Significant Balance of Accounts Receivable

The Company has not experienced any loss on its deposits of cash and cash equivalents. Included in current assets are significant balances of accounts receivable as follows:

	As of December 31,
	2015			2014
Astellas Pharma Inc. (“Astellas”)—Related party		29	%		37	%
AstraZeneca AB (“AstraZeneca”)		71	%		63	%

Collaboration Agreements (Tables)

12 Months Ended

Dec. 31, 2015

Japan [Member]

Summary of Revenue Recognized under Agreement

		Years Ended December 31,
Agreement	Deliverable	2015		2014		2013
Japan	License	$	1,024	$	518	$	566
	Milestones		—		—		12,500
	Total license and milestone revenue	$	1,024	$	518	$	13,066
	Collaboration services revenue*	$	198	$	356	$	433

Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue

The total arrangement consideration has been allocated to each of the following deliverables under the Japan Agreement, along with any associated deferred revenue as follows (in thousands):

	Cumulative Revenue Through December 31, 2015		Deferred Revenue at December 31, 2015		Total Consideration Through December 31, 2015
License	$	42,245	$	—	$	42,245
When and if available compounds		14		28		42
Manufacturing--clinical supplies		1,966		—		1,966
Committee services		16		—		16
Total license and collaboration services revenue	$	44,241	$	28	$	44,269

Europe [Member]

Summary of Revenue Recognized under Agreement

Amounts recognized as revenue under the Europe Agreement were as follows (in thousands):

		Years Ended December 31,
Agreement	Deliverable	2015		2014		2013
Europe	License	$	17,677	$	13,935	$	9,260
	Milestones		—		—		—
	Total license and milestone revenue	$	17,677	$	13,935	$	9,260
	Collaboration services revenue*	$	2,697	$	3,179	$	2,902

Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue

The total arrangement consideration has been allocated to each of the following deliverables under the Europe Agreement, along with any associated deferred revenue as follows (in thousands):

	Cumulative Revenue Through December 31, 2015		Deferred Revenue at December 31, 2015		Total Consideration Through December 31, 2015
License	$	401,316	$	—	$	401,316
When and if available compounds		332		432		764
Manufacturing--clinical supplies		9,612		—		9,612
Development services--in progress		32,154		—		32,154
Committee services		278		—		278
Total license and collaboration services revenue	$	443,692	$	432	$	444,124

U.S./RoW [Member]

Summary of Revenue Recognized under Agreement

Amounts recognized as revenue under the U.S./RoW and China Agreements were as follows (in thousands):

		Years Ended December 31,
Agreement	Deliverable	2015		2014		2013
U.S. / RoW and China	License	$	114,392	$	102,738	$	72,635
	Milestones		15,000		—		—
	Total license and milestone revenue	$	129,392	$	102,738	$	72,635
	Collaboration services revenue*	$	29,731	$	16,820	$	3,843
	China single unit of accounting**	$	—	$	—	$	—

Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue

	Cumulative Revenue Through December 31, 2015		Deferred Revenue at December 31, 2015		Total Consideration Through December 31, 2015
License	$	289,766	$	—	$	289,766
Co-development, information sharing & committee services		50,162		37,936		88,098
Manufacturing--clinical supplies		232		70		302
China-single unit of accounting		—		59,394		59,394
Total license and collaboration services revenue	$	340,160	$	97,400	$	437,560

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Fair Values of Financial Assets Measured on Recurring Basis

The fair values of the Company’s financial assets that are measured on a recurring basis are as follows (in thousands):

	December 31, 2015
	Level 1		Level 2		Level 3		Total
Corporate bonds	$	—	$	126,103	$	—	$	126,103
Bond and mutual funds		25,052		—		—		25,052
Equity investments		197		—		—		197
Money market funds		77,639		—		—		77,639
Certificate of deposits		—		8,215		—		8,215
Total	$	102,888	$	134,318	$	—	$	237,206

	December 31, 2014
	Level 1		Level 2		Level 3		Total
Corporate bonds	$	—	$	158,432	$	—	$	158,432
Equity investments		201		—		—		201
Money market funds		13,802		—		—		13,802
Total	$	14,003	$	158,432	$	—	$	172,435

Fair Values of Financial Liabilities Carried at Historical Cost

The fair values of the Company’s financial liabilities that are carried at historical cost are as follows (in thousands):

	December 31, 2015
	Level 1		Level 2		Level 3		Total
Lease financing obligations	$	—	$	—	$	97,445	$	97,445

	December 31, 2014
	Level 1		Level 2		Level 3		Total
Cease-use liability	$	—	$	—	$	184	$	184
Lease financing obligations		—		—		97,221		97,221
Total	$	—	$	—	$	97,405	$	97,405

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2015

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Cash and Cash Equivalents

Cash and cash equivalents consisted of the following (in thousands):

	December 31,
	2015		2014
Cash	$	75,685	$	151,653
Money market funds		77,639		13,802
Total cash and cash equivalents	$	153,324	$	165,455

Schedule of Property and Equipment

Property and equipment consisted of the following (in thousands):

	December 31,
	2015			2014
Laboratory equipment	$	18,233		$	17,114
Computer equipment		5,701			5,106
Furniture and fixtures		5,361			5,082
Leasehold improvements		93,380			92,790
Building shell (Refer to Note 8)		53,879			53,879
Construction in progress		193			519
Total property and equipment	$	176,747		$	174,490
Less: accumulated depreciation		(47,727	)		(42,319	)
Property and equipment, net	$	129,020		$	132,171

Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Available-for-Sale Investments

	December 31, 2015
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Corporate bonds	$	126,522	$	54	$	(473	)	$	126,103
Certificate of deposits		8,217		—		(2	)		8,215
Bond and mutual funds		25,052		—		—			25,052
Equity investments		126		71		—			197
Total investments	$	159,917	$	125	$	(475	)	$	159,567

	December 31, 2014
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Corporate bonds	$	158,692	$	254	$	(514	)	$	158,432
Equity investments		124		77		—			201
Total investments	$	158,816	$	331	$	(514	)	$	158,633

Summary of Contractual Maturities Available-for-Sale Investments at Fair Value

The contractual maturities of available-for-sale investments were as follows (in thousands):

	December 31,
	2015
Within one year	$	12,797
After one year through four years		121,521
Total debt investments		134,318
Bond and mutual funds		25,052
Equity investments		197
Total investments		159,567

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	December 31,
	2015		2014
Preclinical and clinical trial accruals	$	27,973	$	25,418
Payroll and related accruals		13,535		15,608
Professional services		1,662		2,401
Other		4,762		5,558
Total accrued liabilities	$	47,932	$	48,985

Commitment and Contingencies (Tables)

12 Months Ended

Dec. 31, 2015

Commitments And Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments Under all Non-Cancelable Operating Lease Obligations

Future minimum lease payments under all non-cancelable operating lease obligations as of December 31, 2015 are as follows (in thousands):

Year Ending	Operating Leases
2016	$	128
2017		84
Total minimum payments	$	212

Schedule of Future Minimum Lease Payments on Consolidated Basis Under Company's Facility Financing Lease Obligations

Future minimum lease payments, on a consolidated basis, under the Company’s facility lease financing obligations as of December 31, 2015 are as follows (in thousands):

Year Ending	Lease financing obligations
2016	$	13,699
2017		14,030
2018		14,252
2019		14,468
2020		14,689
Thereafter		41,378
Total minimum payments	$	112,516

Redeemable Convertible Preferred Stock and Equity (Deficit) (Tables)

12 Months Ended

Dec. 31, 2015

Redeemable Convertible Preferred Stock And Equity Deficit [Abstract]

Summary of Common Stock Reserved for Future Issuance

	December 31,
	2015		2014
Common stock outstanding		61,985		59,046
Stock options outstanding		13,583		14,427
RSUs outstanding		865		560
Common stock warrants outstanding		7		173
Shares reserved for future stock options and RSUs grant		3,394		5,358
Shares reserved for future ESPP offering		1,285		1,600
Total shares of common stock reserved		81,119		81,164

Summary of Stock Option Transactions

Stock option transactions, including forfeited options granted under the 2014 Plan as well as prior plans, are summarized below:

	Shares (In thousands)			Weighted Average Exercise per Share		Weighted Average Remaining Contractual Life (In Years)		Aggregate Intrinsic Value (In thousands)
Outstanding at December 31, 2014		14,427		$	7.10
Granted		1,891			27.27
Exercised		(2,362	)		4.28
Expired		(29	)		3.68
Forfeited		(344	)		18.08
Outstanding at December 31, 2015		13,583			10.12		6.07	$	276,401
Vested and expected to vest, December 31, 2015		13,321			9.84		6.01		274,820
Exercisable at December 31, 2015		10,029		$	6.13		5.11	$	244,134

Summary of Restricted Stock Unit Activity

The following table summarizes restricted stock unit activity:

	Number of Shares			Fair Value at Grant
Unvested at December 31, 2014		559,582		$	18.00
Granted		586,008			29.66
Vested		(241,497	)		18.00
Forfeited		(39,244	)		25.08
Unvested at December 31, 2015		864,849		$	25.58

Schedule of Allocated Stock-Based Compensation Expense

	Years Ended December 31,
	2015		2014		2013
Research and development	$	16,987	$	10,893	$	1,925
General and administrative		10,694		7,805		1,519
Total stock-based compensation expense	$	27,681	$	18,698	$	3,444

Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Employee Stock Purchase Plans

The assumptions used to estimate the fair value of stock options granted and ESPPs using the Black-Scholes option valuation model were as follows:

	Years Ended December 31,
	2015			2014			2013
Stock Options
Expected term (in years)		5.2			5.1			4.1
Expected volatility		69.9	%		62.8	%		71.6	%
Risk-free interest rate		1.7	%		1.7	%		0.8	%
Expected dividend yield		—			—			—
Weighted average estimated fair value	$	16.12		$	9.51		$	6.19

ESPPs
Expected term (in years)	1.1 - 1.3				1.2			—
Expected volatility	64.8 - 65.3%			61.7 - 65.5%				—	%
Risk-free interest rate		0.3	%	0.1 - 0.4%				—	%
Expected dividend yield		—			—			—
Weighted average estimated fair value	$	10.54		$	13.22		$	—

Schedule of Warrants to Purchase Shares of Common Stock

The following warrants to purchase shares of Common Stock were issued in connection with certain facility and equipment lease financing arrangements and are outstanding at December 31, 2015:

Year of Issuance	Number of Shares		Exercise Price per Share		Reason for Issuance	Expiration Date
1996		1,600	$	4.38	Issued in connection with lease agreement	Five years after initial public offering or upon merger or sale of the Company’s assets, whichever occurs first
2000		5,538	$	15.00	Issued in connection with lease agreement	Five years after initial public offering or upon merger or sale of the Company’s assets, whichever occurs first
		7,138

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

+ References + Details

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2015

Earnings Per Share [Abstract]

Schedule of Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share

The following securities were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented (in thousands):

	Years Ended December 31,
	2015		2014		2013
Senior Preferred Stock		—		—		15,336
Junior Preferred Stock		—		—		18,584
Employee stock options		13,583		14,427		11,084
RSUs outstanding		865		560		—
Warrants		7		173		173
FibroGen Europe Preferred stock		—		—		959
		14,455		15,160		46,136

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Schedule of Components of Loss Before Income Taxes

The components of loss before income taxes are as follows (in thousands):

	Years Ended December 31,
	2015			2014			2013
Domestic	$	(66,411	)	$	(46,998	)	$	(3,107	)
Foreign		(19,126	)		(12,506	)		(11,836	)
Loss before provision for income taxes	$	(85,537	)	$	(59,504	)	$	(14,943	)

Schedule of Components of Benefit From Income Taxes

The provision for income taxes consists of the following (in thousands):

	Years Ended December 31,
	2015		2014		2013
Current:
Federal	$	—	$	—	$	—
State		2		—		—
Foreign		240		—		—
Total current	$	242	$	—	$	—
Deferred:
Federal	$	—	$	—	$	—
State		—		—		—
Foreign		—		—		—
Total deferred	$	—	$	—	$	—
Total provision from income taxes	$	242	$	—	$	—

Schedule of Reconciliation Between Statutory Federal Income Tax Rate and Effective Tax Rate

The following is the reconciliation between the statutory federal income tax rate and the Company’s effective tax rate:

	Years Ended December 31,
	2015			2014			2013
Tax at statutory federal rate		34.0	%		34.0	%		34.0	%
State tax		—	%		—	%		—	%
Stock-based compensation expense		(4.6	)%		(4.6	)%		(5.7	)%
Net operating losses not benefitted		(21.7	)%		(22.4	)%		(1.6	)%
Foreign net operating losses benefitted		(7.6	)%		(7.1	)%		(26.9	)%
Other		(0.4	)%		0.1	%		0.2	%
Total		(0.3	)%		—	%		—	%

Schedule of Significant Components of Deferred Tax Assets

Significant components of the Company’s deferred tax assets are as follows (in thousands):

	December 31,
	2015			2014
Federal and state net operating loss carryforwards	$	53,393		$	44,748
Tax credit carryforwards		26,620			24,395
Foreign net operating loss carryforwards		8,421			6,485
Stock-based compensation		8,512			5,836
Lease obligations		4,335			5,204
Reserves and accruals		4,891			5,075
Deferred revenue		10,484			3,304
Other		915			950
Subtotal		117,571			95,997
Less: Valuation allowance		(116,718	)		(94,731	)
Net deferred tax assets		853			1,266

Fixed assets		(853	)		(1,266	)
Net deferred tax liabilities		(853	)		(1,266	)
Total net deferred tax assets	$	—		$	—

Schedule of Reconciliation of the Beginning and Ending Amounts of Unrecognized Income Tax Benefits

A reconciliation of the beginning and ending amounts of unrecognized income tax benefits during the years ended December 31, 2013, 2014 and 2015 is as follows (in thousands):

	Federal and State
Balance as of January 1, 2013	$	12,545
Increase due to prior positions		294
Increase due to current year position		680
Balance as of December 31, 2013		13,519
Increase due to prior positions		1,493
Increase due to current year position		4,110
Balance as of December 31, 2014		19,122
Decrease due to prior positions		(2,382	)
Increase due to current year position		7,473
Balance as of December 31, 2015	$	24,213

Segment and Geographic Information (Tables)

12 Months Ended

Dec. 31, 2015

Segment Reporting [Abstract]

Schedule of Revenue by Geographic Area

Geographic revenues, which are based on the bill to region, are as follows (in thousands):

	Years Ended December 31,
	2015		2014		2013
Europe	$	159,123	$	119,559	$	76,478
Japan (related party)		21,596		17,987		25,661
All other		109		55		31
Total revenue	$	180,828	$	137,601	$	102,170

Schedule of Long Lived Assets by Geographic Area

Property and equipment, net by geographic location are as follows (in thousands):

	December 31,
	2015		2014
United States	$	113,628	$	116,099
China		15,392		16,072
Total property and equipment	$	129,020	$	132,171

Schedule of Customer Concentration by Collaboration Partners

	As of or for the Year Ended December 31,
	Percentage of Revenue									Percentage of Accounts Receivable
	2015			2014			2013			2015			2014
Astellas—Related party		12	%		13	%		25	%		29	%		37	%
AstraZeneca		88	%		87	%		75	%		71	%		63	%

The Company - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Nov. 19, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Description [Line Items]
Common stock shares sold	9,315,000
Public offering price	$ 18.00
Net proceeds from initial public offering and concurrent private placement	$ 171,800
Underwriting discounts and commissions	11,700
Offering expenses	4,100
Common stock, aggregate purchase price	$ 20,000	$ 0	$ 20,000	$ 0
Convertible preferred stock converted into shares of common stock	33,919,954	33,919,954
FibroGen Europe [Member]
Business Description [Line Items]
Convertible preferred stock converted into shares of common stock	958,996	1

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) Segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Accounting Policy [Line Items]
Number of operating segment \| Segment	1
Highly liquid investment maturity period	three months or less
Restricted cash	$ 7,254,000	$ 7,254,000
Cash and cash equivalents	$ 153,324,000	$ 165,455,000	$ 76,332,000	$ 38,872,000
Long term Investments Maturity	12 months
Short term investments Maturity	12 months
Impairment of long-lived assets	$ 0
Minimum [Member] \| Computer Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	3 years
Minimum [Member] \| Laboratory Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	3 years
Minimum [Member] \| Furniture and Fixtures [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	3 years
Maximum [Member] \| Computer Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	5 years
Maximum [Member] \| Laboratory Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	5 years
Maximum [Member] \| Furniture and Fixtures [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	5 years
Foreign subsidiaries [Member]
Accounting Policy [Line Items]
Cash and cash equivalents	$ 27,200,000

Summary of Significant Accounting Policies - Schedule of Significant Balance of Accounts Receivable (Detail) - Accounts Receivable [Member] - Credit Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Astellas Agreement [Member]
Accounting Policy [Line Items]
Concentration risk, percentage	29.00%	37.00%
AstraZeneca Agreements [Member]
Accounting Policy [Line Items]
Concentration risk, percentage	71.00%	63.00%

Collaboration Agreements - Astellas Agreements - Additional Information (Detail) - Astellas Agreement [Member] - USD ($) $ in Millions	1 Months Ended		12 Months Ended				35 Months Ended	45 Months Ended
	Apr. 30, 2006	Jun. 30, 2005	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010	Feb. 28, 2009	Feb. 28, 2009
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received								$ 360.1
Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received								$ 40.1
Development and regulatory approval milestones		$ 117.5
Commercial sales milestone		$ 15.0
Additional consideration based on net sales description			Low 20% range
Clinical development milestones				$ 12.5
Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received							$ 320.0
Development and regulatory approval milestones	$ 425.0
Additional consideration based on net sales description			Low 20% range
Clinical development milestones					$ 50.0	$ 40.0
Percentage of joint development costs committed to fund	50.00%

Collaboration Agreements - AstraZeneca Agreements - Additional Information 1 (Detail) - AstraZeneca Agreements [Member] - USD ($) $ in Millions			3 Months Ended	6 Months Ended	12 Months Ended	30 Months Ended
	Dec. 31, 2013	Jul. 30, 2013	Jun. 30, 2015	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2015
U.S./RoW [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expected upfront, non-contingent and time-based payments		$ 374.0
Upfront, non-contingent and time-based payments received				$ 82.0		$ 312.0
Contingent payment		62.0
Development and regulatory approval milestones		550.0
Commercial sales milestone		325.0
Shared development costs		233.0
Additional consideration based on net sales description					Low 20% range
U.S./RoW [Member] \| Development Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Receipt of development milestone payment			$ 15.0
China [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received	$ 16.2
Contingent payment		20.0
Development and regulatory approval milestones		161.0
Commercial sales milestone		167.5
Proceeds from upfront payments		$ 28.2

Collaboration Agreements - Accounting for the Astellas Agreements - Additional Information 2 (Detail) - Astellas Agreement [Member] - USD ($) $ in Millions	1 Months Ended		12 Months Ended	35 Months Ended	45 Months Ended	117 Months Ended
	Apr. 30, 2006	Jun. 30, 2005	Dec. 31, 2015	Feb. 28, 2009	Feb. 28, 2009	Dec. 31, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received					$ 360.1
Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Discount rate applied			17.50%
Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Discount rate applied			20.00%
Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received				$ 320.0
Development costs						$ 124.1
Non-contingent performance period	36 months
Total potential milestones	$ 425.0
Europe [Member] \| Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones	90.0
Europe [Member] \| Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones	335.0
Europe [Member] \| Marketing approval milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones	$ 25.0
Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received					$ 40.1
Total potential milestones		$ 132.5
Commercial sales milestone		15.0
Japan [Member] \| Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones		22.5
Japan [Member] \| Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones		$ 95.0

Collaboration Agreements - Accounting for the AstraZeneca Agreements - Additional Information 3 (Detail) - AstraZeneca Agreements [Member] - USD ($) $ in Millions			6 Months Ended	9 Months Ended	12 Months Ended	30 Months Ended
	Dec. 31, 2013	Jul. 30, 2013	Dec. 31, 2013	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty rate against projected net revenues					40.00%	40.00%
Discount rate applied					17.50%
U.S./RoW [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-contingent performance period		65 months
Expected upfront, non-contingent and time-based payments		$ 374.0
Upfront, non-contingent and time-based payments received			$ 82.0			$ 312.0
Remaining up-front, non-contingent and time-based payments		292.0
Upfront, non-contingent and time-based payments with extended payment terms		230.0
Contingent payment		62.0
Total potential milestones		875.0
Non-substantive milestones		160.0
Commercial sales milestone		325.0
U.S./RoW [Member] \| Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones		65.0
U.S./RoW [Member] \| Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones		325.0
China [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received	$ 16.2
Upfront, non-contingent and time-based payments with extended payment terms		12.0
Contingent payment		20.0
Total potential milestones		328.5
Commercial sales milestone		167.5
Proceeds from upfront payments		28.2
Upfront payments received				$ 12.0
China [Member] \| Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones		15.0
China [Member] \| Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones		$ 146.0

Collaboration Agreements - Summary of Revenue Recognized under Agreement (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total license and milestone revenue	$ 148,093	$ 117,191	$ 94,961
Collaboration services and other revenue from a related party	32,735	20,410	7,209
Revenue recognized	180,828	137,601	102,170
Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenue recognized	159,123	119,559	76,478
Astellas Agreement [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total license and milestone revenue	18,701	14,453	22,326
Collaboration services and other revenue from a related party	2,895	3,535	3,335
Astellas Agreement [Member] \| Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	1,024	518	566
Milestones revenue	0	0	12,500
Total license and milestone revenue	1,024	518	13,066
Collaboration services and other revenue from a related party	198	356	433
Astellas Agreement [Member] \| Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	17,677	13,935	9,260
Milestones revenue	0	0	0
Total license and milestone revenue	17,677	13,935	9,260
Collaboration services and other revenue from a related party	2,697	3,179	2,902
AstraZeneca Agreements [Member] \| China-single unit of accounting [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenue recognized	0	0	0
AstraZeneca Agreements [Member] \| U.S./RoW [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	114,392	102,738	72,635
Milestones revenue	15,000	0	0
Total license and milestone revenue	129,392	102,738	72,635
Collaboration services and other revenue from a related party	$ 29,731	$ 16,820	$ 3,843

Collaboration Agreements - Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue (Detail) $ in Thousands	Dec. 31, 2015 USD ($)
Astellas Agreement [Member] \| Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	$ 44,241
Deferred Revenue	28
Total Consideration	44,269
Astellas Agreement [Member] \| Japan [Member] \| License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	42,245
Deferred Revenue	0
Total Consideration	42,245
Astellas Agreement [Member] \| Japan [Member] \| When and if available compounds [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	14
Deferred Revenue	28
Total Consideration	42
Astellas Agreement [Member] \| Japan [Member] \| Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	1,966
Deferred Revenue	0
Total Consideration	1,966
Astellas Agreement [Member] \| Japan [Member] \| Committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	16
Deferred Revenue	0
Total Consideration	16
Astellas Agreement [Member] \| Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	443,692
Deferred Revenue	432
Total Consideration	444,124
Astellas Agreement [Member] \| Europe [Member] \| License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	401,316
Deferred Revenue	0
Total Consideration	401,316
Astellas Agreement [Member] \| Europe [Member] \| When and if available compounds [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	332
Deferred Revenue	432
Total Consideration	764
Astellas Agreement [Member] \| Europe [Member] \| Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	9,612
Deferred Revenue	0
Total Consideration	9,612
Astellas Agreement [Member] \| Europe [Member] \| Committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	278
Deferred Revenue	0
Total Consideration	278
Astellas Agreement [Member] \| Europe [Member] \| Development services-in progress [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	32,154
Deferred Revenue	0
Total Consideration	32,154
AstraZeneca Agreements [Member] \| U.S./RoW [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	340,160
Deferred Revenue	97,400
Total Consideration	437,560
AstraZeneca Agreements [Member] \| U.S./RoW [Member] \| License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	289,766
Deferred Revenue	0
Total Consideration	289,766
AstraZeneca Agreements [Member] \| U.S./RoW [Member] \| Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	232
Deferred Revenue	70
Total Consideration	302
AstraZeneca Agreements [Member] \| U.S./RoW [Member] \| Co-development, information sharing & committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	50,162
Deferred Revenue	37,936
Total Consideration	88,098
AstraZeneca Agreements [Member] \| U.S./RoW [Member] \| China-single unit of accounting [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	0
Deferred Revenue	59,394
Total Consideration	$ 59,394

Fair Value Measurements - Fair Values of Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	$ 159,567	$ 158,633
Total fair value of financial assets	237,206	172,435
Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	126,103	158,432
Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	25,052
Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	197	201
Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	77,639	13,802
Certificate of deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	8,215
Total fair value of financial assets	8,215
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	102,888	14,003
Level 1 [Member] \| Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 1 [Member] \| Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	25,052
Level 1 [Member] \| Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	197	201
Level 1 [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	77,639	13,802
Level 1 [Member] \| Certificate of deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	134,318	158,432
Level 2 [Member] \| Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	126,103	158,432
Level 2 [Member] \| Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0
Level 2 [Member] \| Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 2 [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	0	0
Level 2 [Member] \| Certificate of deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	8,215
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0	0
Level 3 [Member] \| Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 3 [Member] \| Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0
Level 3 [Member] \| Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 3 [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	0	$ 0
Level 3 [Member] \| Certificate of deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	$ 0

Fair Value Measurements - Fair Values of Financial Liabilities Carried at Historical Cost (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		$ 97,405
Lease financing obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 97,445	97,221
Cease-use liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		184
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		0
Level 1 [Member] \| Lease financing obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	0	0
Level 1 [Member] \| Cease-use liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		0
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		0
Level 2 [Member] \| Lease financing obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	0	0
Level 2 [Member] \| Cease-use liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		0
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		97,405
Level 3 [Member] \| Lease financing obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 97,445	97,221
Level 3 [Member] \| Cease-use liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		$ 184

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value Disclosures [Abstract]
Transfers of assets from level 1 to 2	$ 0	$ 0	$ 0
Transfers of assets from level 2 to 1	0	0	0
Transfers of liabilities from level 1 to 2	0	0	0
Transfers of liabilities from level 2 to 1	0	0	0
Transfers of assets into level 3	0	0	0
Transfers of assets out of level 3	0	0	0
Transfers of liabilities into level 3	0	0	0
Transfers of liabilities out of level 3	$ 0	$ 0	$ 0

Balance Sheet Components - Schedule of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash And Cash Equivalents [Abstract]
Cash	$ 75,685	$ 151,653
Money market funds	77,639	13,802
Total cash and cash equivalents	$ 153,324	$ 165,455	$ 76,332	$ 38,872

Balance Sheet Components - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property and equipment, gross	$ 176,747	$ 174,490
Less: accumulated depreciation	(47,727)	(42,319)
Property and equipment, net	129,020	132,171
Laboratory Equipment [Member]
Property and equipment, gross	18,233	17,114
Computer Equipment [Member]
Property and equipment, gross	5,701	5,106
Furniture and Fixtures [Member]
Property and equipment, gross	5,361	5,082
Leasehold improvements [Member]
Property and equipment, gross	93,380	92,790
Building shell [Member]
Property and equipment, gross	53,879	53,879
Construction in progress [Member]
Property and equipment, gross	$ 193	$ 519

Balance Sheet Components - Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Available-for-Sale Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 159,917	$ 158,816
Gross Unrealized Holding Gains	125	331
Gross Unrealized Holding Losses	(475)	(514)
Estimated Fair Value	159,567	158,633
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	126,522	158,692
Gross Unrealized Holding Gains	54	254
Gross Unrealized Holding Losses	(473)	(514)
Estimated Fair Value	126,103	158,432
Certificate of deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,217
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	(2)
Estimated Fair Value	8,215
Bond and mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25,052
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	0
Estimated Fair Value	25,052
Equity investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	126	124
Gross Unrealized Holding Gains	71	77
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	$ 197	$ 201

Balance Sheet Components - Summary of Contractual Maturities Available-for-Sale Investments at Fair Value(Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investments Schedule [Abstract]
Within one year	$ 12,797
After one year through four years	121,521
Total debt investments	134,318
Bond and mutual funds	25,052
Equity investments	197
Total investments	$ 159,567	$ 158,633

Balance Sheet Components - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accrued Liabilities Current [Abstract]
Preclinical and clinical trial accruals	$ 27,973	$ 25,418
Payroll and related accruals	13,535	15,608
Professional services	1,662	2,401
Other	4,762	5,558
Total accrued liabilities	$ 47,932	$ 48,985

Product Development Obligations - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) DevelopmentObligation	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Number of product development obligations \| DevelopmentObligation	11
Accrued product development costs excluding interest	$ 10.3	$ 11.5
Accrued Interest	$ 4.8	$ 5.0
Bank of Finland Interest Rate [Member]
Debt Instrument [Line Items]
Interest rate percentage	1.00%
Minimum [Member]
Debt Instrument [Line Items]
Interest rate on product development advances	3.00%

Convertible Note Payable - Additional Information (Detail) - FibroGen China [Member] - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2013	Dec. 31, 2015
Debt Instrument [Line Items]
Convertible promissory note	$ 0.6
Interest rate of convertible promissory note	2.00%
Anniversary date of promissory note		8 years

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under all Non-Cancelable Operating Lease Obligations (Detail) $ in Thousands	Dec. 31, 2015 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2016	$ 128
2017	84
Total minimum payments	$ 212

Commitment and Contingencies - Additional Information (Detail) $ in Thousands	1 Months Ended		12 Months Ended
	Feb. 28, 2013 USD ($) ft²	Sep. 30, 2006 USD ($) ft² $ / ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Jun. 30, 2012 USD ($)
Commitments And Contingencies [Line Items]
Restricted cash			$ 7,254	$ 7,254
FibroGen, Inc. [Member]
Commitments And Contingencies [Line Items]
Land subject to leases \| ft²		234,249
Initial term of lease contract		15 years
Restricted cash		$ 7,254
Description of lessee leasing arrangements, operating leases			The agreement included an expansion option to occupy part of an adjacent building within 31 months of the lease commencement date of November 20, 2008.
Lease incentive receivable from land lord through expansion option not used						$ 5,000
Percentage of construction costs for tenant improvement		60.00%
Tenant improvement price per square foot of rental space \| $ / ft²		140.50
Tenant improvements allowance of rental space		$ 32,500
Cost of construction capitalized		50,800
Reimbursements from landlord for tenant improvements		$ 32,500
FibroGen, Inc. [Member] \| South San Francisco [Member]
Commitments And Contingencies [Line Items]
Land subject to sublease \| ft²		106,000
Lease and sublease termination date		Feb. 28, 2015
FibroGen China [Member]
Commitments And Contingencies [Line Items]
Land subject to leases \| ft²	4,820
Initial term of lease contract	8 years
Percentage of construction costs for tenant improvement	100.00%
Cost of construction capitalized	$ 3,100
Reimbursements from landlord for tenant improvements	$ 500
Lease starting date	Feb. 01, 2013
Rent expenses for leased facilities			$ 2,700	2,900	$ 3,000
Sublease income received			$ 3,400	$ 5,000	$ 4,500

Commitment and Contingencies - Schedule of Future Minimum Lease Payments on Consolidated Basis Under Company's Facility Financing Lease Obligations (Detail) $ in Thousands	Dec. 31, 2015 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2016	$ 13,699
2017	14,030
2018	14,252
2019	14,468
2020	14,689
Thereafter	41,378
Total minimum payments	$ 112,516

Redeemable Convertible Preferred Stock and Equity (Deficit) - Convertible Preferred Stock - Additional information (Detail) - $ / shares	Dec. 31, 2015	Dec. 31, 2014	Nov. 19, 2014	Dec. 31, 2013
Class Of Stock [Line Items]
Convertible preferred stock converted into shares of common stock	33,919,954		33,919,954
Convertible Preferred Stock [Member]
Class Of Stock [Line Items]
Authorized Shares				125,000,000
Preferred Stock, par value				$ 0.01
Outstanding convertible preferred stock	0	0

Redeemable Convertible Preferred Stock and Equity (Deficit) - Subsidiary Stock and Non-Controlling Interests - Additional information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Nov. 19, 2014
Class Of Stock [Line Items]
Preferred stock, shares outstanding	0	0
Conversion rights, shares issued upon conversion of each preferred share	33,919,954		33,919,954
Convertible preferred stock converted into shares of common stock	33,919,954		33,919,954
IPO [Member]
Class Of Stock [Line Items]
Conversion rights, shares issued upon conversion of each preferred share			958,996
Convertible preferred stock converted into shares of common stock			958,996
FibroGen Europe [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	42,619,022	42,619,022
Preferred stock redemption percentage	If a Preferred Share can be redeemed by a majority shareholder owning more than ninety percent (90%) of the shares of FibroGen Europe in accordance with the provisions of the Finnish Limited Liability Companies Act, the minority holders of Preferred Shares have the right to request redemption of their shares.
Minimum percentage of shareholder's approval to call for redemption of preferred shares	90.00%
Preferred stock, voting rights	one vote
Conversion rights, shares issued upon conversion of each preferred share	1		958,996
Convertible preferred stock converted into shares of common stock	1		958,996
FibroGen Europe [Member] \| Series A [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,700,845	1,700,845
FibroGen Europe [Member] \| Series B [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,875,000	1,875,000
FibroGen Europe [Member] \| Series C [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,599,503	1,599,503
FibroGen Europe [Member] \| Series D [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,520,141	1,520,141
FibroGen Europe [Member] \| Series E [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	459,565	459,565
FibroGen Europe [Member] \| Series F [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	5,714,332	5,714,332
FibroGen Europe [Member] \| Series G [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	9,927,500	9,927,500
FibroGen Europe [Member] \| Series H [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	19,822,136	19,822,136
FibroGen China [Member]
Class Of Stock [Line Items]
Conversion rights, shares issued upon conversion of each preferred share	1
Convertible preferred stock converted into shares of common stock	1
FibroGen China [Member] \| Series A [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	6,758,000	6,758,000
Preferred shares issued, price per share	$ 1.00
Cash dividend percentage	6.00%

Redeemable Convertible Preferred Stock and Equity (Deficit) - Summary of Common Stock Reserved for Future Issuance (Detail) - shares shares in Thousands	Dec. 31, 2015	Dec. 31, 2014
Class Of Stock [Line Items]
Common stock, shares outstanding	61,985	59,046
Stock options outstanding	13,583	14,427
RSUs outstanding	865	560
Common stock warrants outstanding	7	173
Shares reserved for future stock options and RSUs grant	3,394	5,358
Shares reserved for future ESPP offering	81,119	81,164
ESPP [Member]
Class Of Stock [Line Items]
Shares reserved for future ESPP offering	1,285	1,600

Redeemable Convertible Preferred Stock and Equity (Deficit) - Stock Plans - Additional information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock reserved for issuance		81,119,000	81,164,000
Exercisable, Aggregate Intrinsic Value		$ 244,134
Weighted-average fair value of awards granted		$ 29.66	$ 18.00
Restricted stock units granted				0
2005 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period of stock options		4 years
2005 Stock Plan \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period of stock options		10 years
2014 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period of stock options		5 years
Expiration period of stock options		10 years
Termination date of equity incentive plan		Nov. 12, 2024
Option vesting term		Option vesting schedules are determined by the Company at the time of issuance and generally have a four year vesting schedule (25% vesting on the first anniversary of the vesting base date and quarterly thereafter over the next 3 years).
Number of common stock reserved for issuance		3,393,948
Common stock reserved for future issuance, Description		As of December 31, 2015, the Company has reserved 3,393,948 shares of its common stock for issuance under the 2014 Plan, and shares reserved for issuance will increase January 1 of each year commencing on January 1, 2016 and ending on January 1, 2024 by the lesser of (i) the amount equal to 4% of the number of shares issued and outstanding on December 31 immediately prior to the date of increase or (ii) such lower number of shares as may be determined by the board of directors.
Percentage of common stock reserved for future issuance	4.00%
Number of common stock repurchased		0	0
Exercisable, Aggregate Intrinsic Value		$ 48,700	$ 6,500	$ 300
2014 Equity Incentive Plan \| First Anniversary [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of vesting rights		25.00%
2014 Equity Incentive Plan \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair value exercise price grant date		100.00%

Redeemable Convertible Preferred Stock and Equity (Deficit) - Summary of Stock Option Transactions (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding, Beginning Balance, Shares \| shares	14,427
Granted, Shares \| shares	1,891
Exercised, Shares \| shares	(2,362)
Expired, Shares \| shares	(29)
Forfeited, Shares \| shares	(344)
Outstanding, Ending Balance, Shares \| shares	13,583
Vested and expected to vest, Shares \| shares	13,321
Exercisable, Shares \| shares	10,029
Outstanding, Beginning Balance Weighted Average Exercise per Share \| $ / shares	$ 7.10
Granted, Weighted Average Exercise per Share \| $ / shares	27.27
Exercised, Weighted Average Exercise per Share \| $ / shares	4.28
Expired, Weighted Average Exercise per Share \| $ / shares	3.68
Forfeited, Weighted Average Exercise per Share \| $ / shares	18.08
Outstanding, Ending Balance, Weighted Average Exercise per Share \| $ / shares	10.12
Vested and expected to vest, Weighted Average Exercise per Share \| $ / shares	9.84
Exercisable, Weighted Average Exercise per Share \| $ / shares	$ 6.13
Outstanding, Ending Balance, Weighted Average Remaining Contractual Life	6 years 26 days
Vested and expected to vest, Weighted Average Remaining Contractual Life	6 years 4 days
Exercisable, Weighted Average Remaining Contractual Life	5 years 1 month 10 days
Outstanding, Ending Balance, Aggregate Intrinsic Value \| $	$ 276,401
Vested and expected to vest, Aggregate Intrinsic Value \| $	274,820
Exercisable, Aggregate Intrinsic Value \| $	$ 244,134

Redeemable Convertible Preferred Stock and Equity (Deficit) - Summary of Restricted Stock Unit Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested, Number of Shares, Beginning Balance	560,000
Granted, Number of Shares			0
Unvested, Number of Shares, Ending Balance	865,000	560,000
Granted, Fair value at Grant	$ 29.66	$ 18.00
Restricted Stock Unit [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested, Number of Shares, Beginning Balance	559,582
Granted, Number of Shares	586,008
Vested, Number of Shares	(241,497)
Forfeited, Number of Shares	(39,244)
Unvested, Number of Shares, Ending Balance	864,849	559,582
Unvested, Fair value at Grant, Beginning Balance	$ 18.00
Granted, Fair value at Grant	29.66
Vested, Fair value at Grant	18.00
Forfeited, Fair value at Grant	25.08
Unvested, Fair value at Grant, Ending Balance	$ 25.58	$ 18.00

Redeemable Convertible Preferred Stock and Equity (Deficit) - Employee Stock Purchase Plan - Additional information (Detail) - shares	1 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock reserved for issuance		81,119,000	81,164,000
2014 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase of common stock shares at discount	15.00%
Percentage of fair value exercise price grant date	85.00%
Number of common stock reserved for issuance	1,600,000
Common stock reserved for future issuance, Description		The Company has reserved 1,600,000 shares of its common stock for issuance under the 2014 Purchase Plan and shares reserved for issuance will increase January 1 of each year commencing January 1, 2016 by the lesser of (i) a number of shares equal to 1% of the total number of outstanding shares of common stock on December 31 immediately prior to the date of increase; (ii) 1,200,000 shares or (iii) such number of shares as may be determined by the board of directors.
Percentage of common stock reserved for future issuance	1.00%
Increase in number of shares of common stock reserved for future issuance, shares	1,200,000
Number of common stock repurchased		315,385	0

Redeemable Convertible Preferred Stock and Equity (Deficit) - Schedule of Allocated Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 27,681	$ 18,698	$ 3,444
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	16,987	10,893	1,925
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 10,694	$ 7,805	$ 1,519

Redeemable Convertible Preferred Stock and Equity (Deficit) - Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Employee Stock Purchase Plans (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 2 months 12 days	5 years 1 month 6 days	4 years 1 month 6 days
Expected volatility	69.90%	62.80%	71.60%
Risk-free interest rate	1.70%	1.70%	0.80%
Expected dividend yield	0.00%	0.00%	0.00%
Weighted average estimated fair value	$ 16.12	$ 9.51	$ 6.19
Employee stock purchase plans [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		1 year 2 months 12 days	0 years
Risk-free interest rate	0.30%		0.00%
Expected dividend yield	0.00%	0.00%	0.00%
Weighted average estimated fair value	$ 10.54	$ 13.22	$ 0
Expected volatility, minimum	64.80%	61.70%	0.00%
Expected volatility, maximum	65.30%	65.50%
Employee stock purchase plans [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	1 year 1 month 6 days
Risk-free interest rate		0.10%
Employee stock purchase plans [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	1 year 3 months 18 days
Risk-free interest rate		0.40%

Redeemable Convertible Preferred Stock and Equity (Deficit) - Stock-Based Compensation - Additional information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Stock Option Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs	$ 34.1
Non-vested stock option awards granted that will be recognized on a straight-line basis over the weighted-average period	2 years 3 months 26 days
Restricted Stock Unit [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested stock option awards granted that will be recognized on a straight-line basis over the weighted-average period	2 years 9 months 22 days
Unrecognized compensation costs	$ 16.2

Redeemable Convertible Preferred Stock and Equity (Deficit) - Schedule of Warrants to Purchase Shares of Common Stock (Detail)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Class Of Warrant Or Right [Line Items]
Number of Shares	7,138
Year of Issuance 1996 [Member]
Class Of Warrant Or Right [Line Items]
Year of Issuance	1996
Number of Shares	1,600
Exercise Price per Share \| $ / shares	$ 4.38
Reason for Issuance	Issued in connection with lease agreement
Expiration Date	Five years after initial public offering or upon merger or sale of the Company’s assets, whichever occurs first
Year of Issuance 2000 [Member]
Class Of Warrant Or Right [Line Items]
Year of Issuance	2000
Number of Shares	5,538
Exercise Price per Share \| $ / shares	$ 15.00
Reason for Issuance	Issued in connection with lease agreement
Expiration Date	Five years after initial public offering or upon merger or sale of the Company’s assets, whichever occurs first

Net Loss Per Share - Schedule of Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	14,455	15,160	46,136
Senior Preferred Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	0	0	15,336
Junior Preferred Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	0	0	18,584
Employee stock options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	13,583	14,427	11,084
RSUs outstanding [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	865	560	0
Warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	7	173	173
FibroGen Europe [Member] \| Preferred stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	0	0	959

Income Taxes - Components of Loss Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components Of Income Tax Expense Benefit Continuing Operations [Abstract]
Domestic	$ (66,411)	$ (46,998)	$ (3,107)
Foreign	(19,126)	(12,506)	(11,836)
Loss before income taxes	$ (85,537)	$ (59,504)	$ (14,943)

Income Taxes - Components of Provision From Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
Federal	$ 0	$ 0	$ 0
State	2	0	0
Foreign	240	0	0
Total current	242	0	0
Deferred:
Federal	0	0	0
State	0	0	0
Foreign	0	0	0
Total deferred	0	0	0
Total provision from income taxes	$ 242	$ 0	$ 0

Income Taxes - Reconciliation From Statutory Federal Income Tax Rate to Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Tax at statutory federal rate	34.00%	34.00%	34.00%
State tax	0.00%	0.00%	0.00%
Stock-based compensation expense	(4.60%)	(4.60%)	(5.70%)
Net operating losses not benefitted	(21.70%)	(22.40%)	(1.60%)
Foreign net operating losses benefitted	(7.60%)	(7.10%)	(26.90%)
Other	(0.40%)	0.10%	0.20%
Total	(0.30%)	0.00%	0.00%

Income Taxes - Schedule of Significant Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Components Of Deferred Tax Assets And Liabilities [Abstract]
Federal and state net operating loss carryforwards	$ 53,393	$ 44,748
Tax credit carryforwards	26,620	24,395
Foreign net operating loss carryforwards	8,421	6,485
Stock-based compensation	8,512	5,836
Lease obligations	4,335	5,204
Reserves and accruals	4,891	5,075
Deferred revenue	10,484	3,304
Other	915	950
Subtotal	117,571	95,997
Less: Valuation allowance	(116,718)	(94,731)
Net deferred tax assets	853	1,266
Fixed assets	(853)	(1,266)
Net deferred tax liabilities	(853)	(1,266)
Total net deferred tax assets	$ 0	$ 0

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Change in valuation allowance	$ 22,000,000	$ 21,600,000	$ 2,200,000
Federal and state net operating loss carryforwards	53,393,000	44,748,000
Foreign net operating loss carryforwards	8,421,000	6,485,000
Benefit of stock options	$ 15,800,000
Percentage of ownership changes	0.00%
Unrecognized tax benefits	$ 24,200,000
Accrued interest or penalties, unrecognized tax benefits	$ 0	$ 0
Unrecognized tax benefits description	The Company does not anticipate a material change to its unrecognized tax benefits over the next twelve months that would affect the Company’s effective tax rate.
Earliest Tax Year [Member]
Income Taxes [Line Items]
Foreign statute of limitation generally remains open in the year	2006
Latest Tax Year [Member]
Income Taxes [Line Items]
Foreign statute of limitation generally remains open in the year	2015
Foreign net operating loss [Member]
Income Taxes [Line Items]
Foreign net operating loss carryforwards	$ 35,600,000
Foreign net operating loss [Member] \| Minimum [Member]
Income Taxes [Line Items]
Operating loss carryforwards expiration year	2016
Foreign net operating loss [Member] \| Maximum [Member]
Income Taxes [Line Items]
Operating loss carryforwards expiration year	2025
Federal [Member]
Income Taxes [Line Items]
Federal and state net operating loss carryforwards	$ 185,100,000
Operating loss carryforwards expiration year	2026
Other tax credit carryforwards	$ 27,000,000
Other tax credit carryforwards expiration year	2018
State [Member]
Income Taxes [Line Items]
Federal and state net operating loss carryforwards	$ 270,100,000
Operating loss carryforwards expiration year	2018
State [Member] \| California [Member]
Income Taxes [Line Items]
Other tax credit carryforwards	$ 15,600,000

Income Taxes - Reconciliation of the Beginning and Ending Amounts of Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Ending Balance	$ 24,200
Federal and State [Member]
Income Tax Contingency [Line Items]
Beginning balance	19,122	$ 13,519	$ 12,545
Increase due to prior positions		1,493	294
Decrease due to prior positions	(2,382)
Increase due to current year position	7,473	4,110	680
Ending Balance	$ 24,213	$ 19,122	$ 13,519

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Accounts receivable from related party	$ 4,455	$ 5,033
Accrued liabilities to related parties	2,045	4,594
Goodwin Procter LLP [Member]
Related Party Transaction [Line Items]
Accrued liabilities to related parties		300
Goodwin Procter LLP [Member] \| Intellectual Property [Member]
Related Party Transaction [Line Items]
Payments for legal matters	400
Goodwin Procter LLP [Member] \| Intellectual Property [Member] \| Maximum [Member]
Related Party Transaction [Line Items]
Payments for legal matters		100
Astellas [Member] \| Collaborative Arrangement [Member]
Related Party Transaction [Line Items]
Revenue related to collaboration agreements	21,600	18,000	$ 25,700
Expense related to collaboration agreements	9,800	11,400	$ 4,000
Accounts receivable from related party	4,500	5,000
Accrued liabilities to related parties	$ 2,000	$ 4,300

Segment and Geographic Information - Schedule of Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenue recognized	$ 180,828	$ 137,601	$ 102,170
Europe [Member]
Segment Reporting Information [Line Items]
Revenue recognized	159,123	119,559	76,478
Japan [Member] \| Related Party [Member]
Segment Reporting Information [Line Items]
Revenue recognized	21,596	17,987	25,661
All other [Member]
Segment Reporting Information [Line Items]
Revenue recognized	$ 109	$ 55	$ 31

Segment and Geographic Information - Schedule of Long Lived Assets by Geographic Area (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Revenues From External Customers And Long Lived Assets [Line Items]
Property and equipment, net	$ 129,020	$ 132,171
United States [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Property and equipment, net	113,628	116,099
China [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Property and equipment, net	$ 15,392	$ 16,072

Segment and Geographic Information - Schedule of Customer Concentration by Collaboration Partners (Detail) - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Percentage of Revenue [Member] \| Astellas-Related party [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk, percentage	12.00%	13.00%	25.00%
Percentage of Revenue [Member] \| AstraZeneca [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk, percentage	88.00%	87.00%	75.00%
Percentage of Accounts Receivable [Member] \| Astellas-Related party [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk, percentage	29.00%	37.00%
Percentage of Accounts Receivable [Member] \| AstraZeneca [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk, percentage	71.00%	63.00%

Schedule II - Valuation and Qualifying Accounts (Detail) - Valuation Allowances for Deferred Tax Assets [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 94,731	$ 73,144	$ 70,955
Charged (Credited) to Statement of Operation	21,987	21,587	2,189
Deductions, Net	0	0	0
Balance at End of Year	$ 116,718	$ 94,731	$ 73,144

Redeemable Convertible Preferred Stock and Equity (Deficit) - Common Stock - Additional information (Detail)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Common stock voting rights	one vote

Segment and Geographic Information - Additional information (Detail)	12 Months Ended
	Dec. 31, 2015 Segment
Segment Reporting [Abstract]
Number of operating segment	1