Revenue Recognition - Additional Information (Detail) Milestone in Thousands, $ in Thousands				1 Months Ended			3 Months Ended			9 Months Ended		12 Months Ended
	Oct. 31, 2021 USD ($) $ / shares	Oct. 15, 2020 USD ($) item	May 17, 2018 USD ($) item $ / shares shares	Oct. 31, 2021 USD ($) $ / shares shares	May 31, 2021 USD ($)	Apr. 30, 2013 USD ($) item	Sep. 30, 2021 USD ($) Milestone	Dec. 31, 2020 USD ($) item	Sep. 30, 2020 USD ($) Milestone	Sep. 30, 2021 USD ($) item	Sep. 30, 2020 USD ($) Milestone	Dec. 31, 2020 USD ($) item
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Stock subscription receivable							$ 44,969			$ 44,969
Total revenue							20,272		$ 9,266	22,207	$ 22,993
Regulatory Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from the sale of stock				$ 50,000
License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue							20,031		$ 9,257	21,223	$ 22,377
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
Vifor Agreement [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
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] | Regulatory Milestones [Member] | Subsequent Event [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from milestone payments	$ 15,000
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
VFMCRP Agreement [Member] | License and Milestone Fees | Regulatory Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Receivables							15,000			$ 15,000
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 And VFMCRP Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue, current							0	$ 0		0		$ 0
Other assets							0	0		0		0
Vifor And VFMCRP Agreements [Member] | License and Milestone Fees | Regulatory Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Receivables							20,031			$ 20,031
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]
Deferred revenue, non current							0	0		$ 0		0
Receivables							0	0		0		0
Other assets							$ 0	$ 0		$ 0		$ 0
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
CKDP Agreement [Member] | License and Milestone Fees
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue											$ 626
Number of milestone event probable of occurrence or achieved							0		0	0
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%		20.00%
Proceeds from the sale of stock		$ 50,000		$ 50,000
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			$ 15.23
Stock subscription receivable							$ 44,969			$ 44,969
Premium from sale of stock							5,031			5,031
Potential milestone payments		$ 50,000
Vifor International Ltd. [Member] | Regulatory Milestones [Member] | Subsequent Event [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from the sale of stock				$ 50,000
Stock Issued During Period Shares New Issues | shares				3,282,391
Shares Issued Price Per Share | $ / shares	$ 15.23			$ 15.23
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			5,031
Vifor International Ltd. [Member] | License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue										0
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
Number of combined performance obligations for revenue recognized | item			1
upfront payment			$ 50,000
Premium from sale of stock			$ 5,444
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] | Regulatory Milestones [Member] | Subsequent Event [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from milestone payments				$ 15,000
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			$ 15,000