Business - Additional Information (Detail) $ in Thousands	1 Months Ended			3 Months Ended						9 Months Ended
	Oct. 31, 2021 USD ($) shares	Oct. 31, 2020 USD ($) shares	May 31, 2018 USD ($) shares	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) item	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
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
Upfront and milestone payments received in connection with license agreements				224,100						$ 224,100
Unrestricted cash and cash equivalents and marketable securities				193,415						193,415
Accumulated deficit				447,376						447,376		$ 392,317
Net Loss				$ (1,013)	$ (30,745)	$ (23,301)	$ (16,509)	$ (25,068)	$ (28,922)	(55,059)	$ (70,499)
Net cash used in operating activities										$ (58,842)	$ (87,575)
Vifor International Ltd. [Member]
Nature Of Business [Line Items]
Proceeds from sale of common stock in connection with license agreement		$ 38,449	$ 14,556
Vifor International Ltd. [Member] | Subsequent Event [Member]
Nature Of Business [Line Items]
Proceeds from sale of common stock in connection with regulatory milestone	$ 44,969
Vifor International Ltd. [Member] | Common Stock [Member]
Nature Of Business [Line Items]
Common stock, shares issued | shares		2,939,552	1,174,827
Vifor International Ltd. [Member] | Common Stock [Member] | Subsequent Event [Member]
Nature Of Business [Line Items]
Common stock, shares issued | shares	3,282,391