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Collaboration Agreements and Revenues - AstraZeneca Agreements - Additional Information 1 (Detail) - USD ($)				3 Months Ended	12 Months Ended
	Dec. 29, 2018	Dec. 17, 2018	Jul. 30, 2013	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2015	Jun. 30, 2019
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Unbilled contract asset				$ 2,147,000	$ 2,147,000	$ 180,000,000
Drug product revenue					176,319,000	256,577,000	$ 212,958,000
Accrued long-term co-promotion expenses				27,424,000	27,424,000	53,071,000
Accrued long term co promotion liability current				11,500,000	11,500,000
Deferred revenue ($2,907 and $249 to a related party)				6,547,000	6,547,000	490,000
Drug Product Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue					8,906,000	(36,324,000)	64,776,000
AstraZeneca Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Transaction price and allocated to performance obligations									$ 50,000,000.0
Revenue during period from performance obligations				600,000	$ 600,000	42,400,000
Unbilled contract asset						50,000,000.0
Estimated joint development extended service period					2024
Historical co-promotion costs					$ 0
AstraZeneca Agreements [Member] \| Selling, General and Administrative Expenses [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reversal of accrued co-promotion expenses				84,400,000
Co-promotion expenses					27,200,000
AstraZeneca Agreements [Member] \| Other Noncurrent Liabilities
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accrued long-term co-promotion expenses				27,400,000	27,400,000
AstraZeneca Agreements [Member] \| Accounts Payable [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accrued long term co promotion liability current				16,900,000	16,900,000
AstraZeneca Agreements [Member] \| Accrued Liabilities [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accrued long term co promotion liability current				11,500	11,500
AstraZeneca Agreements [Member] \| Drug Product Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue					4,625,000	0	0
AstraZeneca Agreements [Member] \| U.S./RoW [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent, non-refundable and time-based payments			$ 374,000,000.0
Potential milestone payments			875,000,000.0
Commercial sales milestone			325,000,000.0
Aggregate considerations received excluding drug product revenue				439,000,000.0	$ 439,000,000.0
Shared development costs								$ 233,000,000.0
Additional consideration based on net sales description					low 20% range
Unbilled contract asset						50,000,000.0
Drug product revenue					$ 4,600
AstraZeneca Agreements [Member] \| U.S./RoW [Member] \| FibroGen, Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shared development costs								$ 116,500,000
AstraZeneca Agreements [Member] \| U.S./RoW [Member] \| Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			65,000,000.0
AstraZeneca Agreements [Member] \| U.S./RoW [Member] \| Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			325,000,000.0
AstraZeneca Agreements [Member] \| U.S./RoW [Member] \| Deferred Approval Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			160,000,000.0
AstraZeneca Agreements [Member] \| China [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			348,500,000		22,000,000.0
Drug product revenue					(90,000)	90,000	0
Proceeds from upfront, non-contingent and non-refundable payments			28,200,000
Commercial sales and other events milestone			187,500,000
Aggregate considerations received				77,200,000	77,200,000
Milestone payment received						$ 18,700,000
Milestone payment, revenue recognition	$ 6,000,000.0	$ 6,000,000.0			12,000,000.0		$ 9,900,000
Deferred revenue ($2,907 and $249 to a related party)				7,000,000.0	7,000,000.0
AstraZeneca Agreements [Member] \| China [Member] \| Accrued and Other Current Liabilities [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue ($2,907 and $249 to a related party)				$ 7,000,000.0	$ 7,000,000.0
AstraZeneca Agreements [Member] \| China [Member] \| Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			15,000,000.0
AstraZeneca Agreements [Member] \| China [Member] \| Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			$ 146,000,000.0