INTANGIBLE ASSETS - Summary of Gross Carrying Amounts and net Book Values of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Intangible assets
Gross Carrying Amount	$ 1,098,588	$ 1,098,588
Accumulated amortization	(431,933)	(406,489)
Total	$ 666,655	692,099
Product rights | NUCYNTA
Intangible assets
Remaining Useful Life (In years)	6 years 9 months 18 days
Gross Carrying Amount	$ 1,019,978	1,019,978
Accumulated amortization	(384,466)	(360,891)
Total	$ 635,512	659,087
Product rights | CAMBIA
Intangible assets
Remaining Useful Life (In years)	4 years 9 months 18 days
Gross Carrying Amount	$ 51,360	51,360
Accumulated amortization	(27,175)	(25,891)
Total	$ 24,185	25,469
Product rights | Zipsor
Intangible assets
Remaining Useful Life (In years)	3 years
Gross Carrying Amount	$ 27,250	27,250
Accumulated amortization	(20,292)	(19,707)
Total	$ 6,958	$ 7,543