Intangible Assets - (HETLIOZ) - Additional Information (Detail) - HETLIOZ® - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended	200 Months Ended
	Apr. 30, 2018	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2018	Sep. 30, 2020
Finite-Lived Intangible Assets [Line Items]
Acquisition of intangible assets			$ 8.0	$ 25.0	$ 37.5
Cumulative worldwide sales milestone	$ 250.0
Intangible assets capitalized		$ 25.0			$ 33.0