Revenue Recognition - Disaggregation of Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Total revenue	$ 20,968	$ 41,867	$ 23,028
Maruishi Agreement [Member]
Disaggregation of Revenue [Line Items]
Total revenue	1,449
Other revenue (non-cash)
Disaggregation of Revenue [Line Items]
Total revenue	699
Other revenue (non-cash) | CSL Vifor Kapruvia [Member]
Disaggregation of Revenue [Line Items]
Total revenue	284
Other revenue (non-cash) | Maruishi Agreement [Member]
Disaggregation of Revenue [Line Items]
Total revenue	415
License and milestone fees
Disaggregation of Revenue [Line Items]
Total revenue	910	15,000	21,223
License and milestone fees | CSL Vifor
Disaggregation of Revenue [Line Items]
Total revenue		15,000	20,031
License and milestone fees | Maruishi Agreement [Member]
Disaggregation of Revenue [Line Items]
Total revenue	910	0	1,192
Collaborative revenue
Disaggregation of Revenue [Line Items]
Total revenue	12,936	16,572	706
Collaborative revenue | CSL Vifor Profit Sharing
Disaggregation of Revenue [Line Items]
Total revenue	12,397	16,572
Collaborative revenue | Maruishi Agreement [Member]
Disaggregation of Revenue [Line Items]
Total revenue	539	0	706
Collaborative revenue | Affiliated Entity [Member] | CSL Vifor Profit Sharing
Disaggregation of Revenue [Line Items]
Total revenue	12,397	16,572
Commercial supply revenue
Disaggregation of Revenue [Line Items]
Total revenue	5,843	10,223	701
Commercial supply revenue | Affiliated Entity [Member] | CSL Vifor Korsuva [Member]
Disaggregation of Revenue [Line Items]
Total revenue	5,843	10,223
Clinical compound revenue
Disaggregation of Revenue [Line Items]
Total revenue	165		398
Clinical compound revenue | CSL Vifor (difelikefalin injection) [Member]
Disaggregation of Revenue [Line Items]
Total revenue			361
Clinical compound revenue | Maruishi Agreement [Member]
Disaggregation of Revenue [Line Items]
Total revenue	165	0	37
Royalty revenue
Disaggregation of Revenue [Line Items]
Total revenue	415	72
Royalty revenue | CSL Vifor Kapruvia [Member]
Disaggregation of Revenue [Line Items]
Total revenue	415	72
Royalty revenue | Affiliated Entity [Member] | CSL Vifor
Disaggregation of Revenue [Line Items]
Total revenue	$ 415	$ 72	$ 0