License, Collaboration and Other Significant Agreements - Vifor License Agreement Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended	12 Months Ended
	Feb. 14, 2020	May 31, 2017	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock, issued (in shares)			177,000,963	177,000,963	148,074,085
Deferred revenue, net of current portion			$ 21,474	$ 21,474	$ 25,345
Vifor (International) Ltd. | Research and development
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration purchase payment					$ 10,000
Vifor (International) Ltd. | License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone revenue		$ 25,000		$ 25,000
License agreement, notice period for termination				12 months
Common stock, issued (in shares)		3,571,429
Sale of stock (in dollars per share)		$ 14.00
Proceeds from common stock sold		$ 50,000
Premium over the closing stock price of common stock (in dollars per share)		$ 12.69
Premium amount over the closing stock price of common stock		$ 4,700
Deferred revenue, net of current portion		$ 4,700
Vifor (International) Ltd. | Priority Review Voucher Letter Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from collaborators	$ 10,000		$ 8,600