DEBT (Details)			1 Months Ended				9 Months Ended	12 Months Ended
	Apr. 02, 2015 USD ($)	Sep. 09, 2014 USD ($) D $ / shares	Dec. 31, 2017 USD ($)	Nov. 30, 2017 USD ($)	Apr. 30, 2017 USD ($)	Apr. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Maturity of debt
Payment of a prepayment fee								$ 7,400,000	$ 5,000,000
Loss on prepayment of debt								(5,938,000)	(5,777,000)
Current portion of Senior Notes			$ 82,500,000					82,500,000
Carrying amounts of the liability component
Net carrying amount of the liability component			269,510,000					269,510,000	252,725,000
Net carrying amount of the Notes			274,720,000					274,720,000	466,051,000
Interest expense incurred
Amortization of debt discount and debt issuance costs								19,415,000	17,673,000	$ 15,629,000
Convertible debt			$ 16,135,000					$ 16,135,000	31,706,000
Convertible Notes
Debt
Equity component of convertible debt issued, net of tax		$ 73,300,000
Maturity of debt
Trading days, number | D		20
Business days, period		5 days
Senior Notes
Debt
Aggregate principal amount of notes issued	$ 575,000,000					$ 365,000,000
Effective interest rate (as a percent)			11.09%					11.09%
Proceeds from the issuance of debt	$ 562,000,000
Maturity of debt
2018			$ 82,500,000					$ 82,500,000
2019			120,000,000					120,000,000
2020			80,000,000					80,000,000
2021			82,500,000					82,500,000
Total			365,000,000					365,000,000	475,000,000
Threshold limit to repay principal amount outstanding in full								100,000,000
Threshold limit of asset dispositions which is required to make mandatory prepayments on senior notes								10,000,000
Amount of debt prepaid				$ 10,000,000	$ 100,000,000	100,000,000
Payment of a prepayment fee				$ 400,000	$ 4,000,000	5,000,000		4,400,000
Amendment fee			3,000,000					3,000,000
Loss on prepayment of debt						(5,800,000)		(5,900,000)
Unamortized balances of debt discount and debt issuance costs			1,500,000			$ 800,000		1,500,000
Carrying amounts of the liability component
Principal amount of the Notes			365,000,000					365,000,000	475,000,000
Unamortized debt discount balance			(4,717,000)					(4,717,000)	(8,605,000)
Unamortized debt issuance costs			(3,063,000)					(3,063,000)	(344,000)
Net carrying amount of the Notes			$ 357,220,000					357,220,000	466,051,000
Interest expense incurred
Contractual/Stated coupon interest								44,212,000	54,722,000	46,874,000
Amortization of debt discount and debt issuance costs								2,631,000	2,261,000	1,466,000
Total interest expense								46,843,000	56,983,000	48,340,000
Senior Notes | After Second Anniversary And On Or Prior To Fifth Anniversary
Maturity of debt
Prepayment premium			4.00%
Senior Notes | After Fifth Anniversary
Maturity of debt
Prepayment premium			0.00%
Senior Notes | Other Assets
Debt
Debt issuance costs							$ 500,000
Senior Notes | Three month LIBOR
Debt
Basis spread (as a percent)	9.75%
Interest rate through third anniversary (as a percent)	11.95%
Interest rate after third anniversary (as a percent)	12.95%
Senior Notes | Three month LIBOR | Minimum
Debt
Interest rate (as a percent)	1.00%
Senior Notes | NUCYNTA
Debt
Proceeds from the issuance of debt	$ 550,000,000
Convertible Notes
Debt
Aggregate principal amount of notes issued		$ 345,000,000	$ 345,000,000					$ 345,000,000
Net proceeds from debt offering		334,200,000
Underwriting discount		10,400,000
Offering expenses		$ 400,000
Interest rate (as a percent)		2.50%	2.50%					2.50%
Conversion rate of common stock per $1 of principal amount		0.0519852
Conversion price (in dollars per share) | $ / shares		$ 19.24
Effective interest rate (as a percent)		9.34%
Liability component of debt		$ 226,000,000
Equity component of debt		$ 119,000,000
Maturity of debt
Total			$ 345,000,000					$ 345,000,000	345,000,000
Consecutive trading days, period		30 days
Stock price trigger | $ / shares		$ 25.01
Stock price trigger (as a percent)		130.00%
Consecutive trading-day period		5 days
Principal amount		$ 1,000
Maximum product of the closing sale price of shares of the Company's common stock and the applicable conversion rate for such trading day (as a percent)		98.00%
Observation period		40 days
Carrying amounts of the liability component
Principal amount of the Notes			345,000,000					345,000,000	345,000,000
Unamortized debt discount balance			(71,799,000)					(71,799,000)	(87,570,000)
Unamortized debt issuance costs			(3,691,000)					(3,691,000)	(4,705,000)
Net carrying amount of the Notes			$ 269,510,000					269,510,000	252,725,000
Interest expense incurred
Contractual/Stated coupon interest								8,625,000	8,625,000	8,625,000
Amortization of debt discount and debt issuance costs								16,784,000	15,412,000	14,163,000
Total interest expense								$ 25,409,000	$ 24,037,000	$ 22,788,000
Convertible Notes | Other Assets
Debt
Debt issuance costs		$ 7,100,000
Convertible Notes | Additional Paid-In Capital
Debt
Equity issuance costs		$ 3,700,000