Basis of Presentation and Significant Accounting Policies - Summary of Disaggregated Product Revenue (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 141,421	$ 98,509
FIRDAPSE [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		83,731	66,842
FYCOMPA [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		35,627	30,425
AGAMREE [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	22,042	1,174
Product revenue, net [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 141,400	$ 98,441

[1] *AGAMREE® net product revenue for the three months ended March 31, 2024 is for the period between March 13, 2024 (date of commercial launch) and March 31, 2024.