Business - Additional Information (Detail) $ in Thousands			1 Months Ended	2 Months Ended	12 Months Ended
	Dec. 19, 2024	Jun. 14, 2024	Jan. 31, 2024	Dec. 31, 2023 USD ($)	Dec. 31, 2024 USD ($) item shares	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 17, 2024 USD ($)	Dec. 31, 2021 USD ($)
Nature Of Business [Line Items]
Date of formation					Jul. 02, 2004
Restructuring and related cost, percentage of workforce reduction		70.00%	50.00%
Proceeds from equity and debt financing					$ 520,700
Number of follow-on public offerings | item					4
Net proceeds from the royalty purchase and sale agreement						$ 36,474
Unrestricted cash and cash equivalents and marketable securities					$ 37,903
Accumulated deficit				$ 684,745	755,612	684,745
Net loss					(70,867)	(118,513)	$ (85,474)
Net cash used in operating activities					$ (60,917)	(92,078)	(78,730)
Reverse stock split ratio approval	0.083
Reverse stock split fractional shares issued | shares					0
Stockholders' equity				57,085	$ (4,593)	57,085	$ 158,779		$ 227,522
Vifor Fresenius Medical Care Renal Pharma Ltd Agreement [Member]
Nature Of Business [Line Items]
Asset Purchase Agreement								$ 900
HCR Agreement [Member]
Nature Of Business [Line Items]
Net proceeds from the royalty purchase and sale agreement				36,474		36,474
License Agreement with Maruishi Pharmaceutical Co. Ltd [Member]
Nature Of Business [Line Items]
Earned milestone payment				$ 1,449		$ 1,449
CSL Vifor, Maruishi and CKDP | License and supply agreements for difelikefalin [Member]
Nature Of Business [Line Items]
Amounts earned in connection with license and supply agreements					289,900
Affiliated Entity [Member] | Vifor International Ltd. [Member]
Nature Of Business [Line Items]
Proceeds from the sale of common stock under license agreement with Vifor International					$ 98,000