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 |