Revenue Recognition - Additional Information (Detail) Milestone in Thousands, $ in Thousands			1 Months Ended		3 Months Ended			6 Months Ended		12 Months Ended
	Oct. 15, 2020 item	May 17, 2018 USD ($) item	May 31, 2021 USD ($)	Apr. 30, 2013 USD ($) item	Jun. 30, 2021 USD ($) Milestone	Dec. 31, 2020 USD ($) item	Jun. 30, 2020 USD ($) Milestone	Jun. 30, 2021 USD ($) item	Jun. 30, 2020 USD ($) Milestone	Dec. 31, 2020 USD ($) item
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue							$ 5,634	$ 1,935	$ 13,727
License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue							$ 5,099	1,192	$ 13,120
Royalty [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from contract with customer								0
Collaborative Revenue
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue								$ 706
Vifor Agreement [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue						$ 111,551
Number of remaining performance obligations								0
Number of performance obligations for revenue recognized | item	1					1
upfront payment										$ 100,000
Premium from sale of stock										11,551
Revenue from contract with customer										$ 111,551
VFMCRP Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue		$ 55,444
Number of combined performance obligations for revenue recognized | item		1
Number of remaining performance obligations								0
Number of performance obligations for revenue recognized | item		2
upfront payment		$ 50,000
Premium from sale of stock		$ 5,444
VFMCRP Agreement [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of remaining performance obligations | item								0
Vifor, VFMCRP, and CKDP Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of performance obligations for revenue recognized | item										1
Vifor, VFMCRP, Maruishi and CKDP Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue, non current					$ 0	$ 0		$ 0		$ 0
Receivables					0	0		0		0
Other assets					$ 0	$ 0		$ 0		$ 0
Vifor, Maruishi and CKDP Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
License agreements with IP as separate performance obligation | item								3
Maruishi and CKDP Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of remaining performance obligations | item								0
Maruishi Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of performance obligations for revenue recognized | item				2
Upfront non-refundable, non-creditable license fee and premium from sale of stock				$ 15,337
Number of milestone event probable of occurrence or achieved | Milestone					0		0		0
Maruishi Agreement [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue								$ 1,192
Proceeds from milestone payments			$ 1,898
Maruishi Agreement [Member] | License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated selling price				10,200
Upfront payments on obligations				9,637
Maruishi Agreement [Member] | R&D Services [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated selling price				6,200
Upfront payments on obligations				$ 5,700
Maruishi Agreement [Member] | Collaborative Revenue
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue								$ 706