FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Liabilities:
Convertible Notes, Carrying Value	$ 107,371	$ 105,974
Fair Value, Measurements, Recurring [Member]
Financial Assets:
Deferred compensation assets	1,546	1,743
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Assets:
Deferred compensation assets	407	484
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Assets:
Deferred compensation assets	1,139	1,259
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Assets:
Deferred compensation assets	0	$ 0
Convertible Debt [Member]
Liabilities:
Convertible Notes, Fair Value Disclosure	$ 108,300