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, 2017 USD ($)	Apr. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016 USD ($)
Debt
Payment of a prepayment fee							$ 4,000,000	$ 5,000,000
Loss on prepayment of debt							(5,364,000)	(5,777,000)
Current portion of Senior Notes					$ 57,500,000		57,500,000
Carrying amounts of the liability component
Net carrying amount of the liability component					265,163,000		265,163,000					$ 252,725,000
Net carrying amount of the Notes					311,726,000		311,726,000					466,051,000
Interest expense incurred
Amortization of debt discount and debt issuance costs							14,249,000	13,084,000
Senior Notes
Debt
Aggregate principal amount of notes issued	$ 575,000,000			$ 375,000,000	$ 375,000,000		$ 375,000,000
Debt issuance costs									$ 500,000
Interest rate (as a percent)					2.50%		2.50%
Effective interest rate (as a percent)					11.05%		11.05%			10.90%	10.75%
Proceeds from the issuance of debt	$ 562,000,000
April 2, 2018							$ 57,500,000
April 2, 2019							115,000,000
April 2, 2020							115,000,000
April 2, 2021							87,500,000
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	100,000,000
Payment of a prepayment fee			4,000,000	5,000,000
Loss on prepayment of debt			(5,400,000)	(5,800,000)
Unamortized balances of debt discount and debt issuance costs			$ 1,400,000	$ 800,000
Principal amount					$ 375,000,000		375,000,000
Carrying amounts of the liability component
Principal amount of the Notes					375,000,000		375,000,000					475,000,000
Unamortized debt discount balance					(5,551,000)		(5,551,000)					(8,605,000)
Unamortized debt issuance costs					(223,000)		(223,000)					(344,000)
Net carrying amount of the Notes					369,226,000		369,226,000					466,051,000
Interest expense incurred
Contractual/Stated coupon interest					10,589,000	$ 13,049,000	33,748,000	41,671,000
Amortization of debt discount and debt issuance costs					614,000	581,000	1,811,000	1,663,000
Total interest expense					11,203,000	13,630,000	35,559,000	43,334,000
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%
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					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)			(75,892,000)		(75,892,000)					(87,570,000)
Unamortized debt issuance costs					(3,945,000)		(3,945,000)					(4,705,000)
Net carrying amount of the Notes					265,163,000		265,163,000					$ 252,725,000
Interest expense incurred
Contractual/Stated coupon interest					2,156,000	2,157,000	6,468,000	6,469,000
Amortization of debt discount and debt issuance costs					4,225,000	3,879,000	12,438,000	11,421,000
Total interest expense					$ 6,381,000	$ 6,036,000	$ 18,906,000	$ 17,890,000