Business - Additional Information (Detail) $ in Thousands	1 Months Ended		3 Months Ended				6 Months Ended
	Oct. 31, 2020 USD ($) shares	May 31, 2018 USD ($) shares	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2021 USD ($) item	Jun. 30, 2020 USD ($)	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			203,800				$ 203,800
Unrestricted cash and cash equivalents and marketable securities			207,392				207,392
Accumulated deficit			446,363				446,363		$ 392,317
Net Loss			$ (30,745)	$ (23,301)	$ (25,068)	$ (28,922)	(54,046)	$ (53,990)
Net cash used in operating activities							$ (44,726)	$ (65,955)
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] | Common Stock [Member]
Nature Of Business [Line Items]
Common stock, shares issued | shares	2,939,552	1,174,827