FAIR VALUE OF FINANCIAL INSTRUMENTS - Recurring basis (Details) - Other Long Term Liabilities [Member] - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Liabilities
Deferred Compensation	$ (30,626)	$ (30,928)
Fair Value, Inputs, Level 1 [Member]
Liabilities
Deferred Compensation	(23,506)	(23,476)
Fair Value, Inputs, Level 2 [Member]
Liabilities
Deferred Compensation	0	0
Fair Value, Inputs, Level 3 [Member]
Liabilities
Deferred Compensation	0	0
Measured at Net Asset Value as Practical Expedient [Member]
Liabilities
Deferred Compensation	$ (7,120)	$ (7,452)