Net Sales by Product - Summary of Net Sales by Product (Detail) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Sales Information [Line Items]
Net product sales	$ 18,028	$ 14,156	$ 12,175	$ 11,281	$ 12,510	$ 11,253	$ 8,744	$ 29,478	$ 3,931	$ 3,571	$ 5,004	$ 3,040	$ 55,640	$ 61,985	$ 15,546
BELBUCA [Member]
Sales Information [Line Items]
Net product sales													45,988	26,980
BUNAVAIL [Member]
Sales Information [Line Items]
Net product sales													5,422	7,942	8,266
Product Sales [Member]
Sales Information [Line Items]
Net product sales													$ 51,410	$ 34,922	$ 8,266