DEBT (Details 2) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 23, 2013	Jan. 23, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
DEBT AND FINANCING OBLIGATIONS
Loss on extinguishment of debt			$ 0	$ 0	$ 0	$ 3,398,000
Convertible debt, threshold percentage of stock price trigger			130.00%
Convertible debt, threshold trading days			20
Convertible debt, threshold consecutive trading days			30 days
Estimated conversion value			349,000,000.000		349,000,000.000
Shares issued to settle the conversion premium			3.6
Liability component of convertible debt			120,000,000		120,000,000		120,000,000
Amortization of debt discount					3,104,000	2,924,000
Notes
DEBT AND FINANCING OBLIGATIONS
Debt issued in private placement	120,000,000
Stated interest rate (as a percent)	3.25%	3.25%
Net proceeds from private placement of debt	115,300,000
Principal amount used for debt instrument conversion ratio							1,000
Initial conversion rate of common stock per $1000 of principal amount of Notes (in shares)							0.0402945
Initial conversion price of notes into common stock (in dollars per share)							$ 24.82
Liability component of convertible debt			95,100,000		95,100,000
Total transaction costs related to the issuance of Notes		4,700,000
Term of Notes		6 years
Contractual interest expense			975,000	975,000	2,925,000	2,687,000
Amortization of debt issuance costs			155,000	155,000	465,000	429,000
Amortization of debt discount			1,035,000	1,035,000	3,104,000	2,863,000
Total interest expense recognized			2,165,000	2,165,000	6,494,000	5,979,000
Effective interest rate (as a percent)			7.22%	7.22%	7.22%	7.22%
Notes | Conversion terms, prior to close of business on business day immediately preceding August 1, 2018
DEBT AND FINANCING OBLIGATIONS
Principal amount used for debt instrument conversion ratio			1,000		1,000
Market price per $1000 of principal amount of notes							3.908
Estimated conversion value							3.905
Oxford Credit Facility
DEBT AND FINANCING OBLIGATIONS
Repayment of remaining principal amount of debt	27,500,000
End of term charge on early termination	1,700,000
Prepayment fees on early termination	800,000
Repayment of accrued interest	200,000
Loss on extinguishment of debt	$ 3,400,000