Revenue Recognition - Additional Information (Detail) $ / shares in Units, ¥ in Billions			1 Months Ended					12 Months Ended			44 Months Ended
	Oct. 15, 2020 USD ($) item	May 17, 2018 USD ($) item $ / shares shares	Oct. 31, 2021 USD ($) $ / shares shares	May 31, 2021 USD ($)	Jan. 31, 2021 USD ($)	Apr. 30, 2013 USD ($) item	Apr. 30, 2012 USD ($)	Dec. 31, 2021 USD ($) item contract Milestone	Dec. 31, 2020 USD ($) item	Dec. 31, 2019 USD ($) Milestone	Dec. 31, 2021 USD ($)	Apr. 30, 2013 JPY (¥)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from the sale of common stock										$ 136,498,000
Number of contracts | contract								4
Total revenue								$ 23,028,000	$ 135,082,000	19,886,000
License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue								21,223,000	134,439,000	$ 19,746,000
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								706,000
Vifor Agreement [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue									$ 111,551,000
Number of performance obligations for revenue recognized | item	1								1
upfront payment									$ 100,000,000
Premium from sale of stock									11,551,000
Revenue from contract with customer								111,551,000
Remaining performance obligations								$ 0			$ 0
VFMCRP Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of combined performance obligations for revenue recognized | item		1						1
Number of performance obligations for revenue recognized | item		2
upfront payment		$ 50,000,000
Premium from sale of stock		5,444,000
VFMCRP Agreement [Member] | Regulatory Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from milestone payments			$ 15,000,000
VFMCRP Agreement [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue		$ 55,444,000
Total revenue											55,444,000
Number of performance obligations for revenue recognized | item		1
Remaining performance obligations								$ 0			0
Vifor, VFMCRP, and CKDP Agreements [Member] | License and Milestone Fees
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]
Receivables								$ 0	0		0
Other assets								0	0		0
Deferred revenue								$ 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]
Remaining performance obligations								$ 0			0
Maruishi Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of performance obligations for revenue recognized | item						2
Premium from sale of stock						$ 337,000
Upfront non-refundable, non-creditable license fee and premium from sale of stock						15,337,000
Maruishi Agreement [Member] | Clinical Development and Regulatory Milestones [Member] | Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential milestone payments						10,500,000
Maruishi Agreement [Member] | One-time Sales Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential milestone payments | ¥												¥ 1
Maruishi Agreement [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
License and milestone fees revenue					$ 1,192,000
Proceeds from milestone payments				$ 1,898,000
Maruishi Agreement [Member] | License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated selling price						10,200,000
Upfront payments on obligations						9,637,000
Maruishi Agreement [Member] | R&D Services [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated selling price						6,200,000
Upfront payments on obligations						$ 5,700,000
Maruishi Agreement [Member] | Collaborative Revenue
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue								$ 706,000
CKDP Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of performance obligations for revenue recognized | item								1
Premium from sale of stock							$ 83,000
Number of milestone event probable of occurrence or achieved | Milestone								0		0
CKDP Agreement [Member] | Clinical Development and Regulatory Milestones [Member] | Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential milestone payments							3,750,000
CKDP Agreement [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue									626,000
CKDP Agreement [Member] | License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from contract with customer							$ 646,000
Maruishi Pharmaceutical Co., Ltd. [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of performance obligations for revenue recognized | item						2
Maruishi Pharmaceutical Co., Ltd. [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue								$ 1,192,000
Maruishi Pharmaceutical Co., Ltd. [Member] | Collaborative Revenue
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue								706,000
Vifor International Ltd. [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of performance obligations for revenue recognized | item	1
Vifor International Ltd. [Member] | Regulatory Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Premium on Common Stock Investment, Percentage	20.00%		20.00%
Proceeds from the sale of common stock			$ 50,000,000
Stock Issued During Period Shares New Issues | shares			3,282,391
Stock Issuance Price Measurement Period	30 days		30 days
Shares Issued Price Per Share | $ / shares			$ 15.23
Premium from sale of stock								5,031,000
Proceeds from milestone payments	$ 50,000,000
Vifor International Ltd. [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue								5,031,000	111,551,000
Vifor International Ltd. [Member] | License and Milestone Fees | Regulatory Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Premium from sale of stock								5,031,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Stock Issued During Period Shares New Issues | shares		1,174,827
Shares Issued Price Per Share | $ / shares		$ 17.024
Deferred revenue		$ 55,444,000
Number of combined performance obligations for revenue recognized | item		1
Number of performance obligations for revenue recognized | item		2
upfront payment		$ 50,000,000
Premium from sale of stock		$ 5,444,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] | Regulatory Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from milestone payments			$ 15,000,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] | Regulatory Milestones [Member] | Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential milestone payments								15,000,000			$ 15,000,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue								$ 15,000,000	$ 22,262,000	$ 19,746,000