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) |