INTANGIBLE ASSETS - Schedule of Gross Carrying Amounts and Net Book Value Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,098,588	$ 1,098,588
Accumulated Amortization	(406,489)	(304,715)
Total	$ 692,099	793,873
Product rights | NUCYNTA
Finite-Lived Intangible Assets [Line Items]
Remaining Useful Life (In years)	7 years
Gross Carrying Amount	$ 1,019,978	1,019,978
Accumulated Amortization	(360,891)	(266,590)
Total	$ 659,087	753,388
Product rights | CAMBIA
Finite-Lived Intangible Assets [Line Items]
Remaining Useful Life (In years)	5 years
Gross Carrying Amount	$ 51,360	51,360
Accumulated Amortization	(25,891)	(20,755)
Total	$ 25,469	30,605
Product rights | Zipsor
Finite-Lived Intangible Assets [Line Items]
Remaining Useful Life (In years)	3 years 3 months 18 days
Gross Carrying Amount	$ 27,250	27,250
Accumulated Amortization	(19,707)	(17,370)
Total	$ 7,543	$ 9,880