DEBT (Details)			1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 02, 2015 USD ($)	Sep. 09, 2014 USD ($) item $ / shares	Apr. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Debt
April 2, 2018						$ 57,500,000
April 2, 2019						115,000,000
April 2, 2020						115,000,000
April 2, 2021						143,750,000
April 2, 2022						43,750,000
Payment of a prepayment fee						5,000,000
Loss on prepayment of debt						(5,777,000)
Principal amount				$ 475,000,000		475,000,000
Carrying amounts of the liability component
Net carrying amount of the liability component				248,735,000		248,735,000		$ 237,313,000
Net carrying amount of the Senior Notes				$ 465,453,000		$ 465,453,000		563,012,000
Senior Notes
Debt
Aggregate principal amount of notes issued	$ 575,000,000		$ 475,000,000
Interest rate (as a percent)				2.50%		2.50%
Effective interest rate (as a percent)				10.75%		10.75%
Debt issuance costs								500,000
Proceeds from the issuance of debt	$ 562,000,000
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			100,000,000
Payment of a prepayment fee			5,000,000
Loss on prepayment of debt			(5,800,000)
Unamortized balances of debt discount and debt issuance costs			$ 800,000
Carrying amounts of the liability component
Principal amount of the Notes				$ 475,000,000		475,000,000		575,000,000
Unamortized debt discount balance				(9,180,000)		(9,180,000)		(11,527,000)
Unamortized debt issuance costs				(367,000)		(367,000)		(461,000)
Net carrying amount of the Senior Notes				465,453,000		465,453,000		563,012,000
Interest expense incurred
Contractual/Stated coupon interest				13,049,000	$ 15,796,000	41,671,000	$ 31,078,000
Amortization of debt discount and debt issuance costs				581,000	487,000	1,663,000	958,000
Total interest expense				13,630,000	16,283,000	43,334,000	32,036,000
Senior Notes | Prior to Second Anniversary
Debt
Prepayment premium	5.00%
Senior Notes | After Second Anniversary and on or Prior to Third Anniversary
Debt
Prepayment premium	4.00%
Senior Notes | After Third Anniversary and on or Prior to Fourth Anniversary
Debt
Prepayment premium	3.00%
Senior Notes | After Fourth Anniversary and on or Prior to Fifth Anniversary
Debt
Prepayment premium	2.00%
Senior Notes | After Fifth Anniversary and on or Prior to Sixth Anniversary
Debt
Prepayment premium	1.00%
Senior Notes | After Sixth Anniversary
Debt
Prepayment premium	0.00%
Senior Notes | Three month LIBOR
Debt
Basis spread (as a percent)	9.75%
Debt instrument, floor rate (as a percent)	1.00%
Interest rate through third anniversary (as a percent)	11.95%
Interest rate after third anniversary (as a percent)	12.95%
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		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%
Trading days, number | item		20
Consecutive trading days, period		30 days
Stock price trigger | $ / shares		$ 25.01
Stock price trigger (as a percent)		130.00%
Business days, period		5 days
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
Net carrying amount of the liability component		$ 226,000,000
Principal amount of the Notes				$ 345,000,000		$ 345,000,000		345,000,000
Unamortized debt discount balance		$ (119,000,000)		(91,306,000)		(91,306,000)		(101,965,000)
Unamortized debt issuance costs				(4,959,000)		(4,959,000)		(5,722,000)
Net carrying amount of the Senior Notes				248,735,000		248,735,000		$ 237,313,000
Interest expense incurred
Contractual/Stated coupon interest				2,157,000	2,156,000	6,469,000	6,469,000
Amortization of debt discount and debt issuance costs				3,879,000	3,564,000	11,421,000	10,498,000
Total interest expense				$ 6,036,000	$ 5,720,000	$ 17,890,000	$ 16,967,000