INDEBTEDNESS (Details Textual) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 29, 2017 USD ($)	Feb. 28, 2017 USD ($)	May 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Jun. 30, 2016 USD ($)
Long-term Debt, Gross	$ 143,750				$ 143,750	$ 143,750
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.00%				3.00%
Debt Instrument, Unamortized Discount	$ 13,924				$ 13,924	$ 20,644
Debt Instrument, Interest Rate, Effective Percentage	7.90%				7.90%	7.90%
Amortization of Financing Costs					$ 845	$ 844	$ 844
Line of Credit Facility, Maximum Borrowing Capacity			$ 40,000
Deferred Finance Costs, Net	$ 1,618				1,618	2,463
Interest Income (Expense), Nonoperating, Net					$ (12,035)	(11,327)	(11,008)
Debt Instrument, Covenant Description					no greater than 3.75 to 1.00, a maximum senior secured leverage ratio, which initially shall be no greater than 2.50 to 1.00, and a minimum fixed charge coverage ratio, which shall be greater than or equal to 1.25 to 1.00.
Proceeds from Lines of Credit			30,000
Payments to Acquire Intangible Assets			$ 30,600		$ 97,624	144,494	$ 30,500
Debt Issuance Costs, Noncurrent, Net	1,300				1,300
Unamortized Debt Issuance Expense	200				200
Long-term Debt, Current Maturities	$ 3,353				3,353	$ 0
Short-term Debt, Refinanced, Amount		$ 25,000			25,000
Citizens Bank, N.A. [Member] | Maximum [Member]
Line of Credit Facility, Commitment Fee Percentage	0.35%
Citizens Bank, N.A. [Member] | Minimum [Member]
Line of Credit Facility, Commitment Fee Percentage	0.25%
Senior Secured Credit Facility [Member]
Payments to Acquire Intangible Assets					$ 46,500
Senior Secured Credit Facility [Member] | Citizens Bank, N.A. [Member]
Debt Instrument, Term					5 years
Senior Secured Credit Facility [Member] | Citizens Bank, N.A. [Member] | Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	2.25%
Senior Secured Credit Facility [Member] | Citizens Bank, N.A. [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	1.50%
Citizens Agreement [Member] | Citizens Bank, N.A. [Member]
Deferred Finance Costs, Net	$ 2,700				$ 2,700
Prepaid Expenses and Other Current Assets [Member] | Revolving Credit Facility [Member]
Debt Issuance Costs, Current, Net	200				200
Long Term Debt Current [Member]
Long-term Debt, Gross	3,750				3,750
Debt Issuance Costs, Current, Net	397				397
Long-term Debt, Current Maturities	3,353				3,353
Other Long-Term Assets [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	50,000				50,000
Deferred Finance Costs, Net	1,000				1,000
Debt Issuance Costs, Noncurrent, Net	$ 800				$ 800
Convertible Senior Notes [Member]
Long-term Debt, Gross								$ 143,800
Proceeds from Issuance of Debt								$ 122,600
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.00%				3.00%			3.00%
Underlying Shares Of Common Stock Convertible Debt | shares								2,068,792
Debt Instrument, Convertible, Threshold Trading Days								20
Per Note Principal | $ / shares								$ 1,000
Debt Instrument, Unamortized Discount								$ 33,600
Deferred Offering Costs								$ 5,500
Exercise Price Of Bond Hedge | $ / shares								$ 69.48
Underlying Shares Of Common Stock Bond Hedge | shares							2,068,792	2,068,792
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares							$ 96.21	$ 96.21
Net Adjustments To Additional Paid In Capital Bond Hedge Acquired Warrant Issued Net								$ 15,600
Amortization of Financing Costs								4,200
Payments of Stock Issuance Costs								$ 1,300
Debt Instrument, Convertible, Threshold Consecutive Trading Days								30
Line of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity				$ 30,000
Debt Instrument, Maturity Date				May 12, 2019
Line of Credit Facility, Commitment Fee Percentage				0.25%
Debt Instrument, Description of Variable Rate Basis				LIBOR rate plus 1.25%, 1.50%, or 1.75% per annum, depending upon availability under the Citizens Agreement, or an alternative base rate plus either 0.25%, 0.50%, or 0.75% per annum,
Deferred Finance Costs, Net									$ 300
Interest Income (Expense), Nonoperating, Net					$ 600
Debt Instrument, Covenant Description				1.10 to 1.00
Required Minimum Availability Percentage To Trigger Covenants Line of Credit				12.50%
Required Minimum Availability Balance To Trigger Covenants Line of Credit				$ 3,750
Line Of Credit Facility Additional Revolving Commitment				$ 10,000
Term Loan [Member] | Citizens Bank, N.A. [Member]
Long-term Debt, Gross	$ 75,000				75,000
Debt Instrument, Description of Variable Rate Basis	LIBOR rate plus 1.50% to 2.25% per annum, depending on our total leverage ratio, or an alternative base rate plus an applicable base rate margin, which varies within a range of 0.50% to 1.25%,
Deferred Finance Costs, Net	$ 1,700				1,700
Debt Instrument, Face Amount	75,000				75,000
Debt Instrument, Periodic Payment to be Paid in Installments	3,800				3,800
Long-term Debt, Current Maturities	$ 3,800				$ 3,800
Term Loan [Member] | Citizens Bank, N.A. [Member] | Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	1.25%
Term Loan [Member] | Citizens Bank, N.A. [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	0.50%