REVENUE - Revenue from Commercialization Agreement (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues		$ 55,147	$ 77,493	$ 170,278	$ 269,171
Royalties and milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues		341	20,277	1,226	25,784
Revenue from Transfer of Inventory from Commercialization Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues		0	0	0	55,705
Commercialization Agreement And Amended Commercialization Agreement | Collegium Pharmaceutical Inc
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues		27,300		89,200
Commercialization Agreement And Amended Commercialization Agreement | Collegium Pharmaceutical Inc | Royalties and milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues		30,200	$ 27,800	94,200	$ 87,100
Expense related to third-party royalties		$ (2,900)		$ (5,000)
Performance Obligation Transfer Of Finished Goods | Collegium Pharmaceutical Inc | Revenue from Transfer of Inventory from Commercialization Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues	$ 55,700