EMPLOYEE BENEFIT PLANS - Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net (losses) gains	$ (1,587)	$ (1,514)	$ (1,743)
Amortization of losses (gains)	861	449	673
Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net (losses) gains	(207)	(285)	149
Amortization of losses (gains)	$ 8	$ 0	$ 2