Agreements - Summary of Aggregate Amount Paid for the Assets Acquired (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]
Base cash payment	160,000
Cash paid for pro-rated prepaid expenses	1,576
Reimbursement on base purchase price	(3,238)	[1]
Transaction costs	5,870	[2]
Total purchase consideration	$ 164,208

[1] Recorded in prepaid expenses and other current assets in the accompanying consolidated balance sheet as of the acquisition date and reimbursement was fully applied as of June 30, 2023

[2] As of September 30, 2023 the full $5.9 million has been paid in cash