REVENUE - Commercialization Agreement (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues	$ 34,565		$ 55,147	$ 76,099	$ 170,278
Royalties and milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues	$ 299		341	$ 1,158	1,226
Collegium Pharmaceutical Inc | Amended Commercialization Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues		$ 11,300
Contract asset, amortization		1,800
Collegium Pharmaceutical Inc | Amended Commercialization Agreement | Royalties and milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues		$ 13,100
Expense related to third-party royalties			$ 2,900		$ 5,000