Business - Additional Information (Detail) $ in Thousands	1 Months Ended		3 Months Ended								12 Months Ended
	Oct. 31, 2020 USD ($) shares	May 31, 2018 USD ($) shares	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) item	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares
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			201,893								$ 201,893
Proceeds from sale of common stock in connection with license agreement											38,449		$ 14,556
Unrestricted cash and cash equivalents and marketable securities			251,490								251,490
Accumulated deficit			392,317				$ 400,727				392,317	$ 400,727
Net income (loss)			$ 78,909	$ (16,509)	$ (25,068)	$ (28,922)	$ (28,611)	$ (32,842)	$ (22,960)	$ (21,960)	8,410	(106,373)	(74,013)
Net cash used in operating activities											$ (5,487)	$ (109,225)	$ (22,301)
Common Stock [Member]
Nature Of Business [Line Items]
Common stock, shares issued | shares												6,325,000	5,175,000
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