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EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS Pension Costs (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]    
Defined Benefit Plan, Plan Assets, Contributions by Employer $ 100  
Service cost 1,347 $ 1,068
Interest cost 1,066 962
Expected return on plan assets (1,540) (1,368)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (12) (49)
Net periodic benefit cost 861 613
Pension Plan [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Other Nonoperating Gains (Losses) $ (500) $ (500)