Business - Additional Information (Detail) $ in Thousands		1 Months Ended	3 Months Ended							9 Months Ended
	Jun. 14, 2024	Jan. 31, 2024	Sep. 30, 2024 USD ($) item	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Sep. 30, 2024 USD ($) item	Sep. 30, 2023 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							$ 520,700
Number of follow-on public offerings | item			4							4
Unrestricted cash and cash equivalents and marketable securities			$ 42,036							$ 42,036
Accumulated deficit			747,933			$ 684,745				747,933
Net loss			$ (12,476)	$ (20,016)	$ (30,696)		$ (28,032)	$ (31,479)	$ (26,665)	(63,188)	$ (86,176)
Net cash used in operating activities										(56,874)	$ (74,708)
HCR Agreement [Member]
Nature Of Business [Line Items]
Net proceeds from the royalty purchase and sale agreement						$ 36,474
CSL Vifor, Maruishi and CKDP | License and supply agreements for difelikefalin [Member]
Nature Of Business [Line Items]
Payments received in connection with license and supply agreements										288,600
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