Basis of Presentation and Significant Accounting Policies - Summary of Disaggregated Product Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 102,688	$ 57,244	$ 287,636	$ 153,446
FIRDAPSE [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	66,224	57,173	188,648	153,255
FYCOMPA [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	36,393	0	98,750	0
Product revenue, net [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 102,617	$ 57,173	$ 287,398	$ 153,255