LONG TERM DEBT AND CREDIT AGREEMENT (Details) - USD ($)								3 Months Ended	12 Months Ended
	May 13, 2019	Apr. 08, 2019	Jan. 22, 2019	Dec. 15, 2017	Mar. 14, 2017	Feb. 26, 2016	Jun. 15, 2015	Jun. 30, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 09, 2019	Dec. 03, 2018	Feb. 08, 2018	Nov. 09, 2017
Line of Credit Facility [Line Items]
Other Long-term Debt, Noncurrent									$ 1,296,000	$ 1,453,000
Term Loan, net									200,105,000	122,811,000
Convertible Notes Payable									28,187,000	97,731,000
Short-term Debt, Fair Value									30,554,000	1,405,000
Long-term Debt									199,034,000	220,590,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments	$ 600,000
Repayments of Debt	72,700,000		$ 3,600,000	$ 1,700,000					14,700,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt									$ (577,000)	(74,000)	$ (5,000)
Gain (Loss) on Extinguishment of Debt	(2,900,000)
ConvertibleDebtRetired			3,900	2,000					16,247			73,986	96,133
ConvertibleDebtIssued			106,753				125,000							123,000
Extinguishment of Debt, Amount	$ 74,000,000.0		$ 3,900,000	$ 2,000,000.0					$ 16,200,000
Capped Call Transaction Cost Reimbursement									27,000	16,000	$ 4,000
Debt, Long-term and Short-term, Combined Amount									229,588,000
Payments of Debt Issuance Costs		$ 1,600,000
Debt Related Commitment Fees and Debt Issuance Costs		$ 4,400,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net									4,014,000
Cerberus Business Finance LLC [Member]
Line of Credit Facility [Line Items]
Long-term Debt															$ 115,000,000.0
Line of Credit Facility, Frequency of Payments						We 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 also requires us 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		On April 8, 2019, we entered into an amendment to the Financing Agreement. The amendment provides for an additional delayed draw term loan commitment in the aggregate principal amount of $100.0 million (the “Delayed Draw Funds”) for the purpose of funding the purchase of a portion of the Notes in a tender offer. On May 2, 2019, we received the Delayed Draw Funds under the Financing Agreement. We used $72.7 million of the Delayed Draw Funds for the purchase of a portion of the Notes, $0.6 million for the Notes interest payment, and $6.0 million for the payment of refinancing fees. On June 18, 2019, we repaid $20.7 million of the Delayed Draw Funds. The $79.3 million Delayed Draw Funds borrowed will mature on May 10, 2023 under the Financing Agreement. The amendment also modified the covenant that requires us to maintain a leverage ratio (defined to mean the ratio of (a) the sum of indebtedness under the Term Loan and Credit Facility and non-cash collateralized letters of credit to (b) consolidated EBITA) based on the level of availability of our Credit Facility plus unrestricted cash on-hand.			The Financing Agreement contains customary representations and warranties, covenants, mandatory prepayments, and events of default under which our payment obligations may be accelerated.
additional long term debt															15,000,000.0
Long-term Debt [Member] | Cerberus Business Finance LLC [Member]
Line of Credit Facility [Line Items]
Unamortized Debt Issuance Expense									3,334,000	2,613,000
Interest Expense, Long-term Debt									16,000,000.0
Convertible Debt [Member]
Line of Credit Facility [Line Items]
Short-term Debt, Fair Value									28,187,000
Long-term Debt									0
Long-term Debt, Gross							$ 125,000,000.0
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)									3,300,000	6,400,000
Interest Expense, Debt									4,400,000	8,800,000
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 our failure to deliver certain documents or reports to the Trustee, our 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 Redemption [Table Text Block]							The Notes are senior unsecured obligations. Upon the occurrence of certain specified fundamental changes, the holders may require us 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.
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net									$ 680,000	$ 9,022,000
Convertible Debt [Member] | Capped call [Member]
Line of Credit Facility [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 us when and if the Notes are converted.
Capped Call Transaction Costs								$ 10,100,000
Long-term Debt [Member] | Cerberus Business Finance LLC [Member]
Line of Credit Facility [Line Items]
Long-term Debt, Gross						$ 100,000,000.0
Line of Credit [Member] | Cerberus Business Finance LLC [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity						$ 5,000,000.0									$ 10,000,000.0
Convertible Debt [Member]
Line of Credit Facility [Line Items]
Convertible Notes Payable Transaction Costs							$ 4,700,000
Convertible Debt [Member] | Interest Expense [Member]
Line of Credit Facility [Line Items]
Convertible Notes Payable Transaction Costs							3,600,000
Convertible Debt [Member] | Equity [Member]
Line of Credit Facility [Line Items]
Convertible Notes Payable Transaction Costs							$ 1,100,000