Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2020 item	Dec. 31, 2021 USD ($) item segment Institution	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($) lease	Dec. 31, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of suppliers		3
Cost of goods sold | $		$ 0
Prepaid R&D expense | $		$ 1,481	$ 11,286
Expected dividend yield		0.00%	0.00%	0.00%
Stockholders' equity | $		$ 227,522	$ 249,001	$ 186,713		$ 133,630
Number of operating segments | segment		1
Commercial Supply Revenue
Summary Of Significant Accounting Policies [Line Items]
Number of parties in net profit sharing arrangement		2
Vifor, VFMCRP, and CKDP Agreements [Member] | License and Milestone Fees
Summary Of Significant Accounting Policies [Line Items]
Number of performance obligations for revenue recognized		1
Stamford Operating Lease [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of renewable terms		1
Operating Lease, renewable term		5 years
Stamford Operating Lease [Member] | ASC 842 [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of operating lease | lease					2
Number of renewable terms		1
Operating Lease, renewable term		5 years
Annual incremental borrowing rate		7.00%
Stamford Operating Lease [Member] | ASC 842 [Member] | Cumulative Effect, Period of Adoption, Adjustment
Summary Of Significant Accounting Policies [Line Items]
Stockholders' equity | $					$ 0
New Stamford Lease [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of renewable terms	1
Operating Lease, renewable term	5 years
Annual incremental borrowing rate		7.00%
New Stamford Lease [Member] | ASC 842 [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of renewable terms		1
Operating Lease, renewable term		5 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Period that would require for locating and qualifying alternate sources if the suppliers fail to meet supply commitments		2 years
Options [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected life of options (in years)		6 years 3 months	6 years 3 months	6 years 3 months
Expected dividend yield		0.00%	0.00%	0.00%
Cash And Cash Equivalents And Marketable Securities [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of financial institutions | Institution		3