EMPLOYEE BENEFIT PLANS - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net losses	$ (25,043)	$ (24,317)
Deferred income tax benefit	1,216	1,216
AOCI	(23,827)	(23,101)
Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net losses	(491)	(292)
Deferred income tax benefit	6	6
AOCI	$ (485)	$ (286)