Business - Additional Information (Detail) $ in Thousands		1 Months Ended			3 Months Ended
	Aug. 23, 2021	Oct. 31, 2021 USD ($) shares	Oct. 31, 2020 USD ($) shares	May 31, 2018 USD ($) shares	Mar. 31, 2022 USD ($) item	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Nature Of Business [Line Items]
Date of formation					Jul. 02, 2004
Proceeds from equity and debt financing					$ 519,600
Number of follow-on public offerings | item					4
Payments received in connection with license agreements					$ 229,710
Unrestricted cash and cash equivalents and marketable securities					209,567
Accumulated deficit					508,507		$ 480,758
Net loss					(27,749)	$ (23,301)
Net cash used in operating activities					$ (25,525)	$ (23,721)
Vifor Agreement [Member]
Nature Of Business [Line Items]
Percentage of net profit sharing	60.00%		60.00%
Vifor International Ltd. [Member]
Nature Of Business [Line Items]
Proceeds from sale of common stock in connection with license agreement			$ 38,449	$ 14,556
Proceeds from sale of common stock in connection with regulatory milestone		$ 44,969
Vifor International Ltd. [Member] | Vifor Agreement [Member]
Nature Of Business [Line Items]
Percentage of net profit sharing	40.00%		40.00%
Common stock, shares issued | shares			2,939,552
Vifor International Ltd. [Member] | Regulatory Milestones [Member]
Nature Of Business [Line Items]
Common stock, shares issued | shares		3,282,391
Vifor International Ltd. [Member] | Common Stock [Member]
Nature Of Business [Line Items]
Common stock, shares issued | shares		3,282,391	2,939,552	1,174,827