EMPLOYEE BENEFITS - Amounts Recognized as a Component of Other Comprehensive Income (loss) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Recognition of loss due to settlement		$ (215)	$ 0	$ 0
Net loss occurring during the year		593	9,816	1,994
Net prior service cost occurring during the year	$ 163	163	0	0
Defined Benefit Pension Plan
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Recognition of net loss		2,474	1,827	1,512
Recognition of prior service (credit) cost		(14)	(14)	(14)
Recognition of loss due to settlement		0	0	0
Net loss occurring during the year		(1,086)	(6,070)	(1,581)
Net prior service cost occurring during the year		151	0	0
Total adjustment during the year		1,525	(4,257)	(83)
Deferred tax (expense) benefit		(320)	894	17
Other comprehensive income (loss), net of tax		1,205	(3,363)	(66)
Defined Benefit Pension Plan Acquired
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Recognition of net loss		10	0	0
Recognition of prior service (credit) cost		0	0	0
Recognition of loss due to settlement		215	0	0
Net loss occurring during the year		(124)	(427)	(69)
Net prior service cost occurring during the year		0	0	0
Total adjustment during the year		101	(427)	(69)
Deferred tax (expense) benefit		(21)	90	14
Other comprehensive income (loss), net of tax		80	(337)	(55)
Restoration Plan
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Recognition of net loss		551	559	677
Recognition of prior service (credit) cost		7	6	7
Recognition of loss due to settlement		0	0	0
Net loss occurring during the year		617	(3,319)	(344)
Net prior service cost occurring during the year		12	0	0
Total adjustment during the year		1,187	(2,754)	340
Deferred tax (expense) benefit		(249)	578	(71)
Other comprehensive income (loss), net of tax		$ 938	$ (2,176)	$ 269