EMPLOYEE BENEFITS - Amounts Recognized as a Component of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Pension Plan
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Abstract]
Net loss	$ (31,783)	$ (33,171)
Prior service cost	0	(137)
Accumulated other comprehensive (loss) income, before tax	(31,783)	(33,308)
Deferred tax benefit	6,674	6,994
Accumulated other comprehensive (loss) income, net of tax	(25,109)	(26,314)
Defined Benefit Pension Plan Acquired
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Abstract]
Net loss	(498)	(598)
Prior service cost	0	0
Accumulated other comprehensive (loss) income, before tax	(498)	(598)
Deferred tax benefit	104	125
Accumulated other comprehensive (loss) income, net of tax	(394)	(473)
Restoration Plan
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Abstract]
Net loss	(5,575)	(6,744)
Prior service cost	0	(18)
Accumulated other comprehensive (loss) income, before tax	(5,575)	(6,762)
Deferred tax benefit	1,171	1,419
Accumulated other comprehensive (loss) income, net of tax	$ (4,404)	$ (5,343)