FAIR VALUE - Narrative (Details) - USD ($)		12 Months Ended
	Nov. 08, 2018	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Aug. 13, 2019	Nov. 30, 2017	Sep. 09, 2014
Convertible debt
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Interest rate		2.50%
Lazanda
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Liabilities, contingent consideration						$ 200,000
Commercialization Agreement | Collegium Pharmaceutical Inc
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Warrant, fair value price (in dollars per share)	$ 15.56		$ 17.17
Collegium Pharmaceutical Inc | Commercialization Agreement
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Warrant, expected term	4 years		3 years 10 months 10 days
Warrant, risk-free rate	3.05%		2.48%
Warrant, remaining contractual period			3 years 10 months 10 days
Convertible Senior Notes, 2.5% | Convertible debt
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Interest rate							2.50%
Par value of debt				$ 145,000,000.0			$ 345,000,000.0
Convertible Senior Notes, 2.5% | Convertible debt | Level 2
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Par value of debt		$ 145,000,000	$ 345,000,000
Convertible Senior Notes, 2.5% | Convertible debt | Fair Value | Level 2
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Estimated fair value of debt		108,100,000	$ 231,800,000
Convertible Senior Notes, 5.0% | Convertible debt
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Interest rate					5.00%
Estimated fair value of debt					$ 98,400,000
Par value of debt					$ 120,000,000.0
Convertible Senior Notes, 5.0% | Convertible debt | Level 2
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Interest rate					5.00%
Par value of debt		120,000,000
Convertible Senior Notes, 5.0% | Convertible debt | Fair Value | Level 2
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Estimated fair value of debt		81,600,000
Other (expense) income, net | Collegium warrants
Schedule of Cash and Cash Equivalents and Marketable Securities [Line Items]
Gain (loss) for fair value of warrants		$ 800,000