EMPLOYEE BENEFITS - Change in Projected Benefit Obligation and Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Pension Plan
Change in Projected Benefit Obligation:
Benefit obligation at end of prior year	$ 100,012	$ 85,992	$ 94,276
Service cost	1,793	1,420	1,548
Interest cost	3,031	3,654	3,392
Actuarial loss (gain)	11,892	12,763	(9,399)
Benefits Paid	(6,596)	(3,703)	(3,622)
Expenses paid	(202)	(114)	(203)
Curtailments	(13,082)	0	0
Settlements	0	0	0
Benefit obligation at end of year	96,848	100,012	85,992
Change in Plan Assets:
Fair value of plan assets at end of prior year	93,818	84,911	91,233
Actual return	3,399	12,724	(4,497)
Employer contributions	0	0	2,000
Benefits paid	(6,596)	(3,703)	(3,622)
Expenses paid	(202)	(114)	(203)
Settlements	0	0	0
Fair value of plan assets at end of year	90,419	93,818	84,911
(Un)Funded status at end of year	(6,429)	(6,194)	(1,081)
Accrued benefit (liability) asset recognized	(6,429)	(6,194)	(1,081)
Accumulated benefit obligation at end of year	96,848	88,247	77,888
Defined Benefit Pension Plan Acquired
Change in Projected Benefit Obligation:
Benefit obligation at end of prior year	4,870	3,873	4,392
Service cost	0	0	0
Interest cost	162	169	163
Actuarial loss (gain)	437	943	(480)
Benefits Paid	(51)	(68)	(183)
Expenses paid	(113)	(47)	(19)
Curtailments	0	0	0
Settlements	(1,601)	0	0
Benefit obligation at end of year	3,704	4,870	3,873
Change in Plan Assets:
Fair value of plan assets at end of prior year	4,763	4,070	4,031
Actual return	615	808	(259)
Employer contributions	0	0	500
Benefits paid	(51)	(68)	(183)
Expenses paid	(113)	(47)	(19)
Settlements	(1,601)	0	0
Fair value of plan assets at end of year	3,613	4,763	4,070
(Un)Funded status at end of year	(91)	(107)	197
Accrued benefit (liability) asset recognized	(91)	(107)	197
Accumulated benefit obligation at end of year	3,704	4,870	3,873
Restoration Plan
Change in Projected Benefit Obligation:
Benefit obligation at end of prior year	19,098	15,300	14,642
Service cost	429	339	293
Interest cost	568	713	597
Actuarial loss (gain)	1,344	3,319	344
Benefits Paid	(688)	(573)	(576)
Expenses paid	0	0	0
Curtailments	(1,962)	0	0
Settlements	0	0	0
Benefit obligation at end of year	18,789	19,098	15,300
Change in Plan Assets:
Fair value of plan assets at end of prior year	0	0	0
Actual return	0	0	0
Employer contributions	688	573	576
Benefits paid	(688)	(573)	(576)
Expenses paid	0	0	0
Settlements	0	0	0
Fair value of plan assets at end of year	0	0	0
(Un)Funded status at end of year	(18,789)	(19,098)	(15,300)
Accrued benefit (liability) asset recognized	(18,789)	(19,098)	(15,300)
Accumulated benefit obligation at end of year	$ 18,789	$ 16,258	$ 13,403