LONG TERM DEBT AND CREDIT AGREEMENT (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 15, 2015
Principal Amount	$ 125,000		$ 125,000		$ 125,000
Unamortized debt discount	(28,298)		(28,298)
Debt issuance costs	(3,412)		(3,412)		4,400
Convertible Notes Payable Accumulated Accretion	207		207
Net Carrying Value	$ 93,497		$ 93,497		$ 96,700
Accounts Payable, Interest-bearing, Interest Rate					2.00%
Debt Instrument, Convertible, Terms of Conversion Feature	The Notes are convertible into cash, shares of the Company’s common stock or a combination of cash and shares of common stock, at the Company’s election, based on an initial conversion rate, subject to adjustment, of 45.5840 shares per $1,000 principal amount of Notes, which is equal to an initial conversion price of $21.94 per share.		The Notes are convertible into cash, shares of the Company’s common stock or a combination of cash and shares of common stock, at the Company’s election, based on an initial conversion rate, subject to adjustment, of 45.5840 shares per $1,000 principal amount of Notes, which is equal to an initial conversion price of $21.94 per share. Prior to December 15, 2019, the Notes are convertible only in the following circumstances: (1) during any calendar quarter commencing after September 30, 2015, if the last reported sale price of the Company’s common stock is greater than or equal to 130% of the applicable conversion price for at least 20 trading days during a period of 30 consecutive trading days ending on the last trading day of the preceding calendar quarter; (2) during the five business day period after any five consecutive trading day period (the “Measurement Period”) in which the trading price per $1,000 principal amount of notes for each trading day in the Measurement Period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on such trading day; or (3) upon the occurrence of specified corporate transactions.
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments			$ 28,300
Debt Instrument, Interest Rate, Effective Percentage					7.66%
Interest Expense	$ 920	$ 415	1,292	$ 788
Increase (Decrease) in Deferred Income Taxes			$ 6,514	16
Debt Instrument, Call Feature			The Capped Call has a strike price of $21.94 and a cap price of $26.00 and is exercisable by the Company when and if the Notes are converted.
Net Proceeds from Issuance of Convertible Notes Payable					$ 120,600
Line of Credit Facility, Interest Rate Description			Interest accrues on outstanding borrowings under the Credit Facility at a rate of a Eurodollar Rate (as defined in the Credit Facility) plus 2.00% or a Base Rate (as defined in the Credit Facility) plus 1.00%, at the option of the Company. The Company must also pay to the Lenders, on a quarterly basis, an unused line fee at a rate of 0.25% per annum on an amount equal to (1) the average lending commitments under the Credit Facility during the immediately preceding quarter less (2) the average daily amount of the outstanding borrowings plus the undrawn amount of any outstanding letters of credit under the Credit Facility during the immediately preceding quarter. During the term of the Credit Facility, the Company is entitled to reduce the maximum amounts of the Lenders’ commitments, subject to the payment of certain fees based on the amount of any reduction.
Capped Call Transaction Costs			$ (10,125)	$ 0
Debt [Member]
Debt issuance costs					3,400
Equity [Member]
Debt issuance costs					$ 1,000
Convertible Debt [Member]
Interest Expense	$ 200