FAIR VALUE MEASUREMENT (Details) $ in Thousands	Dec. 31, 2017 USD ($) insurance_policy	Dec. 31, 2016 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of life insurance policies | insurance_policy	70
Life insurance policies, net face value	$ 43,400
Cash surrender value of life insurance policies	18,300	$ 15,700
Deferred compensation assets	18,400	15,900
Deferred compensation plan | Estimate of Fair Value, Fair Value Disclosure
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	95	188
Total fair value	95	188
Deferred compensation plan | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	95	188
Total fair value	$ 95	$ 188