INDEBTEDNESS (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 28, 2017	Jun. 30, 2016
Long-term Debt, Gross		$ 143,750	$ 143,750
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		3.00%
Debt Instrument, Unamortized Discount		$ 20,644	$ 27,016
Debt Instrument, Interest Rate, Effective Percentage		7.90%	7.80%
Amortization of Financing Costs		$ 844	$ 844
Deferred Finance Costs, Net		2,463	3,307
Interest Income (Expense), Nonoperating, Net		(11,327)	$ (11,008)	$ (787)
Subsequent Event [Member]
Line of Credit Facility, Maximum Borrowing Capacity					$ 40,000
Long-term Line of Credit					$ 30,000
Prepaid Expenses and Other Current Assets [Member]
Deferred Costs, Current		300
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%
Underlying Shares Of Common Stock Convertible Debt				2,068,792
Debt Instrument, Convertible, Conversion Price				$ 69.48
Debt Instrument, Convertible, Threshold Trading Days				20
Debt Instrument Percent Of Conversion Price				130.00%
Per Note Principal				$ 1,000
Debt Instrument, Unamortized Discount				$ 33,600
Deferred Offering Costs				$ 5,500
Exercise Price Of Bond Hedge				$ 69.48
Underlying Shares Of Common Stock Bond Hedge			2,068,792	2,068,792
Class of Warrant or Right, Exercise Price of Warrants or Rights			$ 96.21	$ 96.21
Net Adjustments To Additional Paid In Capital Bond Hedge Acquired Warrant Issued Net				$ 15,600
Debt Instrument, Convertible, Threshold Consecutive Trading Days				30 days
Amortization of Financing Costs				$ 4,200
Payments of Stock Issuance Costs				$ 1,300
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		$ 65
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