Stock-Based Compensation - Stock Option Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	$ 80	$ 81	$ 319	$ 314
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	29	29	169	111
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	51	52	150	203
Stock Options | Cara Therapeutics, Inc.
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	1,100	1,733	6,290	11,607	$ 13,648
Stock Options | Research and Development [Member] | Cara Therapeutics, Inc.
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense		504	1,016	5,973	7,222
Stock Options | General and Administrative [Member] | Cara Therapeutics, Inc.
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	$ 1,100	$ 1,229	$ 5,274	$ 5,634	$ 6,426