Net Sales by Product - Summary of Net Sales by Product (Detail) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	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, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net product sales	$ 42,168	$ 39,443	$ 36,582	$ 38,278	$ 31,637	$ 30,306	$ 29,677	$ 19,769	$ 18,028	$ 14,156	$ 12,175	$ 11,281	$ 156,471	$ 111,389	$ 55,640
BELBUCA
Segment Reporting Information [Line Items]
Net product sales													136,128	97,538	45,988
Symproic
Segment Reporting Information [Line Items]
Net product sales													14,709	8,061	0
BUNAVAIL
Segment Reporting Information [Line Items]
Net product sales													3,737	2,289	5,422
Product Sales
Segment Reporting Information [Line Items]
Net product sales													$ 154,574	$ 107,888	$ 51,410
Revenue | Product Concentration Risk | BELBUCA
Segment Reporting Information [Line Items]
Concentration risk percentage													88.10%	90.40%	89.50%
Revenue | Product Concentration Risk | Symproic
Segment Reporting Information [Line Items]
Concentration risk percentage													9.50%	7.50%	0.00%
Revenue | Product Concentration Risk | BUNAVAIL
Segment Reporting Information [Line Items]
Concentration risk percentage													2.40%	2.10%	10.50%