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EMPLOYEE BENEFIT PLANS Table - Net Periodic Benefit Cost (Income) (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Pension Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 2,405 $ 2,239 $ 7,216 $ 6,717
Interest cost 1,206 1,127 3,618 3,381
Expected return on assets (1,854) (1,603) (5,563) (4,808)
Amortization of prior service credit (515) (515) (1,543) (1,546)
Amortization of net loss 544 371 1,631 1,113
Net periodic benefit cost (income) 1,786 1,619 5,359 4,857
Other Postretirement Benefits Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 126 115 378 341
Interest cost 107 107 322 323
Expected return on assets 0 0 0 0
Amortization of prior service credit (286) (286) (859) (858)
Amortization of net loss 53 47 160 143
Net periodic benefit cost (income) $ 0 $ (17) $ 1 $ (51)