CONVERTIBLE SENIOR NOTES (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended	3 Months Ended
Jul. 27, 2010	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Convertible senior notes
Net carrying amount of the liability component		$ 117,180		$ 115,881
Non-cash interest expense recognized		1,299	1,179
Non-cash deferred financing amortization costs included in interest expense		2,220	1,835
2010 Notes
Convertible senior notes
Proceeds from Convertible Debt	125,000
Carrying amount of the equity component (additional paid-in capital)		24,375		24,375
Principal amount of the 2010 Notes		125,000		125,000
Unamortized discount of the liability component		7,820		9,119
Net carrying amount of the liability component		117,180		115,881
Effective interest rate on liability component (as a percent)		10.00%	10.00%
Cash interest expense recognized		1,541	1,541
Non-cash interest expense recognized		1,299	1,179
Non-cash deferred financing amortization costs included in interest expense		$ 177	$ 177
Remaining period over which the unamortized discount will be recognized		1 year 4 months 17 days

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of noncash expense included in interest expense to issue debt and obtain financing associated with the related debt instruments. Alternate captions include noncash interest expense.

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Carrying value as of the balance sheet date of the portion of long-term debt due within one year or the operating cycle if longer identified as Convertible Notes Payable. Convertible Notes Payable is a written promise to pay a note which can be exchanged for a specified amount of another, related security, at the option of the issuer and the holder.

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The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

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Remaining amortization period for discount on the liability component of convertible debt which may be settled in cash upon conversion, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Face (par) amount of debt instrument at time of issuance.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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The cash inflow from the issuance of a long-term debt instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder.

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