Segment Reporting - Summary of Net Sales by Product (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Sales Information [Line Items]
Net product sales	$ 34,922	$ 8,266	$ 4,157
BELBUCA [Member]
Sales Information [Line Items]
Net product sales	26,980	0
BUNAVAIL [Member]
Sales Information [Line Items]
Net product sales	$ 7,942	$ 8,266	$ 4,157