Net Sales by Product - Summary of Net Sales by Product (Detail) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	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, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net product sales	$ 31,637	$ 30,306	$ 29,677	$ 19,769	$ 18,028	$ 14,156	$ 12,175	$ 11,281	$ 12,510	$ 11,253	$ 8,744	$ 29,478	$ 111,389	$ 55,640	$ 61,985
BELBUCA
Segment Reporting Information [Line Items]
Net product sales													97,538	45,988	26,980
Symproic
Segment Reporting Information [Line Items]
Net product sales													8,061	0	0
BUNAVAIL
Segment Reporting Information [Line Items]
Net product sales													2,289	5,422	7,942
Product Sales
Segment Reporting Information [Line Items]
Net product sales													$ 107,888	$ 51,410	$ 34,922
Sales Revenue, Net | Product Concentration Risk | BELBUCA
Segment Reporting Information [Line Items]
Percentage of amount due to major vendors accounts payable													90.40%	89.50%	77.30%
Sales Revenue, Net | Product Concentration Risk | Symproic
Segment Reporting Information [Line Items]
Percentage of amount due to major vendors accounts payable													7.50%	0.00%	0.00%
Sales Revenue, Net | Product Concentration Risk | BUNAVAIL
Segment Reporting Information [Line Items]
Percentage of amount due to major vendors accounts payable													2.10%	10.50%	22.70%