Business - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	May 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Nature Of Business [Line Items]
Date of formation		Jul. 02, 2004
Proceeds from equity and debt financing		$ 383,200
Upfront and milestone payments received in connection with license agreements		88,900
Unrestricted cash and cash equivalents and marketable securities		156,140
Accumulated deficit		316,314		$ 294,354
Net loss		21,960	$ 16,767
Net cash used in operating activities		$ 27,526	$ 18,468
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