FAIR VALUE OF FINANCIAL INSTRUMENTS - Recurring basis (Details) - Other Long Term Liabilities [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Liabilities
Deferred Compensation	$ (40,995)	$ (10,875)
Fair Value, Inputs, Level 1 [Member]
Liabilities
Deferred Compensation	(23,751)	(10,875)
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	$ (17,244)	$ 0