Business - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) item	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)
Nature Of Business [Line Items]
Date of formation	Jul. 02, 2004
Proceeds from equity and debt financing	$ 520,700
Number of follow-on public offerings | item	4
Unrestricted cash and cash equivalents and marketable securities	$ 69,773
Accumulated deficit	715,441	$ 684,745
Net loss	(30,696)		$ (26,665)
Net cash used in operating activities	(30,453)		$ (34,618)
HCR Agreement [Member]
Nature Of Business [Line Items]
Net proceeds from the royalty purchase and sale agreement	$ 36,474	$ 36,474
Minimum [Member]
Nature Of Business [Line Items]
Expected approvals and commercial launches period	12 months
Maximum [Member]
Nature Of Business [Line Items]
Expected approvals and commercial launches period	18 months
CSL Vifor, Maruishi and CKDP | License and supply agreements for difelikefalin
Nature Of Business [Line Items]
Payments received in connection with license and supply agreements	$ 288,600
Affiliated Entity [Member] | Vifor International Ltd.
Nature Of Business [Line Items]
Proceeds from the sale of common stock under license agreement with Vifor International	$ 98,000