Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 60,941	$ 60,941
Accumulated Amortization	36,399	34,872
Net Carrying Amount	$ 24,542	$ 26,069
HETLIOZ®
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated future useful life	2035-02	2034-05
Gross Carrying Amount	$ 33,000	$ 33,000
Accumulated Amortization	8,458	6,931
Net Carrying Amount	$ 24,542	$ 26,069
Fanapt®
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life	2016-11	2016-11
Gross Carrying Amount	$ 27,941	$ 27,941
Accumulated Amortization	27,941	27,941
Net Carrying Amount	$ 0	$ 0