LONG TERM DEBT AND CREDIT AGREEMENT (Details) - USD ($)							3 Months Ended		12 Months Ended
	Feb. 08, 2018	Dec. 15, 2017	Nov. 09, 2017	Mar. 14, 2017	Feb. 26, 2016	Jun. 15, 2015	Dec. 31, 2017	Jun. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Credit Facilities [Line Items]
Other Long-term Debt, Noncurrent										$ 0
Term Loan, net							$ 102,751,000		$ 102,751,000	92,208,000
Convertible Notes Payable							105,974,000		105,974,000	101,587,000
Short-term Debt, Fair Value							5,906,000		5,906,000	5,000,000
Long-term Debt							204,498,000		204,498,000	188,795,000
Repayments of Debt		$ 1,700,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt									(5,000)
ConvertibleDebtRetired		2,000
ConvertibleDebtIssued		123,000				125,000
Extinguishment of Debt, Amount		$ 2,000,000
Capped Call Transaction Cost Reimbursement									4,000
Capped Call Transaction Costs									0	0	$ (10,125,000)
Repayments of Lines of Credit									0	30,000,000	$ 65,500,000
Cerberus Business Finance LLC [Member]
Credit Facilities [Line Items]
Long-term Debt			$ 115,000,000
Line of Credit, Interest Rate Terms				On March 14, 2017 (the “Amendment No. 1 Effective Date”), the Company entered into an amendment (the “First Amendment”) to the Financing Agreement. Following the Amendment No. 1 Effective Date, interest accrues on outstanding borrowings under the credit facility and the term loan (each as defined in the Financing Agreement) at a rate of either the LIBOR Rate (as defined in the Financing Agreement) plus 7.25% or a Reference Rate (as defined in the Financing Agreement) plus 6.25%, at the option of the Company. The Company must also pay to the Lenders, on a monthly basis, an unused line fee at a rate of 0.5% per annum.
Line of Credit Facility, Frequency of Payments					The Company may prepay all or any portion of the Term Loan prior to its stated maturity, subject to the payment of certain fees based on the amount repaid. The Term Loan requires quarterly principal payments of $1.25 million commencing in June 2016. The Term Loan also requires the Company to use 50% of excess cash, as defined in the Financing Agreement, to repay outstanding principal of the loans under the Financing Agreement
Debt Instrument, Covenant Description				The Financing Agreement contains customary representations and warranties, covenants, mandatory prepayments, and events of default under which the Company’s payment obligations may be accelerated. The First Amendment modified the covenant requiring the Company to maintain a Leverage Ratio (defined to mean the ratio of (a) total funded indebtedness to (b) consolidated EBITDA) such that following the Amendment No. 1 Effective Date, the Company is required to maintain a Leverage Ratio of no greater than 3.50:1.00 for the four quarters ended March 31, 2017, 4.20:1.00 for the four quarters ended June 30, 2017, 4.75:1.00 for the four quarters ended September 30, 2017, 4.80:1.00 for the four quarters ended December 31, 2017, 4.40:1.00 for each of the four quarters ending March 31, 2018 through March 31, 2019, respectively, and thereafter declining over time from 3.50:1.00 to 2.50:1.00. The Financing Agreement also restricts the Company from making capital expenditures in excess of $20 million in any fiscal year. As of December 31, 2017, the Company was in compliance with these covenants.
Line of Credit Facility, Collateral					The Company granted a security interest on substantially all of its assets to secure the obligations under the Credit Facility and the Term Loan.
Debt Instrument, Restrictive Covenants					The Financing Agreement contains restrictive covenants that are customary for an agreement of this kind, including, for example, covenants that restrict the Company from incurring additional indebtedness, granting liens, making investments and restricted payments, making acquisitions, paying dividends and engaging in transactions with affiliates.
additional long term debt			15,000,000
Debt Instrument, Periodic Payment			187,500
Long-term Debt [Member] | Cerberus Business Finance LLC [Member]
Credit Facilities [Line Items]
Long-term Debt					$ 100,000,000
Interest Expense, Debt							2,200,000		8,200,000
Line of Credit [Member] | Cerberus Business Finance LLC [Member]
Credit Facilities [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding							$ 0		0
Convertible Debt [Member]
Credit Facilities [Line Items]
Long-term Debt, Gross		$ 123,000,000				$ 125,000,000
Net Proceeds from Issuance of Convertible Notes Payable						120,300,000
Convertible Debt, Noncurrent						96,700,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments						$ 28,300,000
Debt Instrument, Interest Rate, Stated Percentage						2.00%
Debt Instrument, Interest Rate, Effective Percentage						7.66%
Amortization of Debt Discount (Premium)									6,100,000	5,600,000
Interest Expense, Debt									$ 8,600,000	$ 8,100,000
Debt Instrument, Interest Rate Terms						The Notes pay interest semi-annually on June 15 and December 15 of each year, beginning on December 15, 2015, at an annual rate of 2.00% and mature on June 15, 2020 unless earlier converted or repurchased in accordance with their terms prior to such date. Additional interest may be payable upon the occurrence of certain events of default relating to the Company’s failure to deliver certain documents or reports to the Trustee, the Company’s failure to timely file any document or report required pursuant to Section 13 or 15(d) of the Exchange Act or if the Notes are not freely tradable as of one year after the last date of original issuance of the Notes.
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. 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. On or after December 15, 2019 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their Notes at any time, regardless of the foregoing circumstances. The Company may not redeem the Notes prior to their maturity, which means that the Company is not required to redeem or retire the Notes periodically.
Debt Instrument Redemption [Table Text Block]						The Notes are senior unsecured obligations. Upon the occurrence of certain specified fundamental changes, the holders may require the Company to repurchase all or a portion of the Notes for cash at 100% of the principal amount of the Notes being purchased, plus any accrued and unpaid interest.
Convertible Debt [Member] | Capped call [Member]
Credit Facilities [Line Items]
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.
Capped Call Transaction Costs								$ 10,100,000
Long-term Debt [Member] | Cerberus Business Finance LLC [Member]
Credit Facilities [Line Items]
Long-term Debt, Gross					100,000,000
Line of Credit [Member] | Cerberus Business Finance LLC [Member]
Credit Facilities [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 10,000,000		$ 5,000,000
Convertible Debt [Member]
Credit Facilities [Line Items]
Convertible Notes Payable Transaction Costs						$ 4,700,000
Convertible Debt [Member] | Interest Expense [Member]
Credit Facilities [Line Items]
Convertible Notes Payable Transaction Costs						3,600,000
Convertible Debt [Member] | Equity [Member]
Credit Facilities [Line Items]
Convertible Notes Payable Transaction Costs						$ 1,100,000
Subsequent Event [Member]
Credit Facilities [Line Items]
Repayments of Debt	$ 1,700,000
ConvertibleDebtRetired	2,000
ConvertibleDebtIssued	123,000
Extinguishment of Debt, Amount	$ 2,000,000