Business - Additional Information (Detail) $ in Thousands		1 Months Ended			3 Months Ended				6 Months Ended
	May 17, 2018 USD ($) shares	Oct. 31, 2021 USD ($) shares	Oct. 31, 2020 USD ($) shares	May 31, 2018 USD ($) shares	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Jun. 30, 2022 USD ($) item	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Nature Of Business [Line Items]
Date of formation									Jul. 02, 2004
Proceeds from equity and debt financing					$ 519,600				$ 519,600
Number of follow-on public offerings | item									4
Payments received in connection with license and supply agreements					252,700				$ 252,700
Unrestricted cash and cash equivalents and marketable securities					204,683				204,683
Accumulated deficit					512,713				512,713		$ 480,758
Net loss					$ (4,206)	$ (27,749)	$ (30,745)	$ (23,301)	(31,955)	$ (54,046)
Net cash used in operating activities									$ (30,028)	$ (44,726)
Vifor Agreement No 1 [Member]
Nature Of Business [Line Items]
Percentage of net profit sharing			60.00%
Vifor Agreement No 2 [Member]
Nature Of Business [Line Items]
Percentage of net profit sharing				50.00%
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 No 1 [Member]
Nature Of Business [Line Items]
Percentage of net profit sharing			40.00%
Common stock, shares issued | shares			2,939,552
Vifor International Ltd. [Member] | Vifor Agreement No 2 [Member]
Nature Of Business [Line Items]
Common stock, shares issued | shares	1,174,827
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
Vifor [Member] | Vifor Agreement No 2 [Member]
Nature Of Business [Line Items]
Percentage of net profit sharing				50.00%
Non-refundable, non-creditable upfront payment	$ 50,000