FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible Notes Payable, Noncurrent	$ 95,600
Liabilities:
Convertible Notes, Carrying Value	95,570	$ 97,731
Fair Value, Measurements, Recurring [Member]
Financial Assets:
Deferred compensation assets	1,430	1,372
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Assets:
Deferred compensation assets	312	386
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Assets:
Deferred compensation assets	1,118	986
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	$ 96,700