REVENUE - Revenue from Commercialization Agreement (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues		$ 57,203	$ 63,274	$ 115,132	$ 191,678
Royalties and milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues		263	5,257	886	5,507
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		31,000		61,900
Commercialization Agreement And Amended Commercialization Agreement | Collegium Pharmaceutical Inc | Royalties and milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues		31,900	$ 31,200	64,000	$ 59,300
Expense related to third-party royalties		$ (1,000)		$ (2,100)
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