Business - Additional Information (Detail) $ in Thousands		1 Months Ended	3 Months Ended					6 Months Ended
	Jun. 14, 2024	Jan. 31, 2024	Jun. 30, 2024 USD ($) item	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Jun. 30, 2024 USD ($) item	Jun. 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			$ 56,618					$ 56,618
Accumulated deficit			735,457		$ 684,745			735,457
Net loss			(20,016)	$ (30,696)		$ (31,479)	$ (26,665)	(50,712)	$ (58,144)
Net cash used in operating activities								$ (42,890)	$ (55,063)
HCR Agreement [Member]
Nature Of Business [Line Items]
Net proceeds from the royalty purchase and sale agreement					$ 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					$ 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