Commitments and Contingencies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) ft² Extension_Option	Dec. 31, 2016 USD ($)	Jul. 31, 2016 ft²
Commitments And Contingencies [Line Items]
Area of property leased | ft²	3,384		45,362
Monthly lease payments	$ 242,000
Operating lease payments commencement date	Jan. 01, 2017
Landlord contributions accounted for deferred lease incentive	$ 2,169,920
Landlord contribution for leasehold improvements	$ 70,526
Sublease term	2 years
Frequency of sublease rent receivable	monthly
Sublease monthly rent receivable	$ 22,000
Operating lease obligations partially offset by future sublease payments	257,000
Rent expense associated with lease	3,200,000	$ 2,500,000
Contract cost incurred in research and development activities	52,400,000
Total remaining contract costs	$ 276,400,000
FibroGen, Inc. | Minimum
Commitments And Contingencies [Line Items]
Expected appeal process period	2 years
FibroGen, Inc. | Maximum
Commitments And Contingencies [Line Items]
Expected appeal process period	3 years
Office Space
Commitments And Contingencies [Line Items]
Lease expiration date	Sep. 11, 2026
Lease period, number of extension options | Extension_Option	1
Lease extension period	5 years
Lab Space
Commitments And Contingencies [Line Items]
Lease expiration date	Nov. 30, 2021
Lease period, number of extension options | Extension_Option	1
Lease extension period	2 years
Other Assets
Commitments And Contingencies [Line Items]
Total security deposit in connection with lease	$ 1,280,857	1,280,857
Other Current Assets
Commitments And Contingencies [Line Items]
Total security deposit in connection with lease	21,432	21,432
Other Liabilities
Commitments And Contingencies [Line Items]
Total security deposit liability in connection with sublease	21,432	$ 21,432
Lease Monthly Payments On Or About January 1 2017
Commitments And Contingencies [Line Items]
Monthly lease payments	$ 22,000