FAIR VALUE OF FINANCIAL INSTRUMENTS - Recurring basis (Details) - Other Long Term Liabilities [Member] - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Liabilities
Deferred Compensation	$ (33,804)	$ (40,995)
Fair Value, Inputs, Level 1 [Member]
Liabilities
Deferred Compensation	(28,873)	(23,751)
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	$ (4,931)	$ (17,244)