Agreements - Summary of Total Purchase Price Allocated to Acquired Assets (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($)
Asset Acquisition [Line Items]
Total purchase consideration	$ 94,978
U.S. Rights for FYCOMPA [Member]
Asset Acquisition [Line Items]
Inventory	4,100
Prepaid expenses and other current assets (samples)	130
Prepaid commercialization expenses	1,576
Property and equipment, net	433
License and acquired intangibles for FYCOMPA®	158,143
Accrued preclinical and clinical trial expenses	(174)
Total purchase consideration	$ 164,208