Business - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	May 31, 2018	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Nature Of Business [Line Items]
Date of formation		Jul. 02, 2004
Proceeds from equity and debt financing		$ 519,600
Upfront and milestone payments received in connection with license agreements		89,000
Unrestricted cash and cash equivalents and marketable securities		179,764
Accumulated deficit		429,649		$ 400,727
Net loss		28,922	$ 21,960
Net cash used in operating activities		$ (38,303)	$ (27,526)
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member]
Nature Of Business [Line Items]
Proceeds from sale of common stock in connection with license agreement	$ 14,556
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] | Common Stock [Member]
Nature Of Business [Line Items]
Common stock, shares issued	1,174,827