INTANGIBLE ASSETS - Summary of Gross Carrying Amounts and net Book Values of Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Intangible assets
Gross Carrying Amount	$ 1,098,588	$ 1,098,588
Accumulated Amortization	(482,820)	(406,489)
Total	$ 615,768	692,099
Product rights | NUCYNTA
Intangible assets
Remaining Useful Life (In years)	6 years 2 months 12 days
Gross Carrying Amount	$ 1,019,978	1,019,978
Accumulated Amortization	(431,617)	(360,891)
Total	$ 588,361	659,087
Product rights | CAMBIA
Intangible assets
Remaining Useful Life (In years)	4 years 2 months 12 days
Gross Carrying Amount	$ 51,360	51,360
Accumulated Amortization	(29,743)	(25,891)
Total	$ 21,617	25,469
Product rights | Zipsor
Intangible assets
Remaining Useful Life (In years)	2 years 6 months
Gross Carrying Amount	$ 27,250	27,250
Accumulated Amortization	(21,460)	(19,707)
Total	$ 5,790	$ 7,543