RETIREMENT AND POSTRETIREMENT PLANS - Funded status of the Employee Retirement Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Plans [Member]
Reconciliation of projected benefit obligation:
Acquired in the Merger	$ 33,897
Service cost	893
Interest cost	609
Actuarial gain	(304)
Benefit payments	(600)
Projected benefit obligation at end of year	34,495
Plan assets at fair value (investments in trust funds managed by trustee)
Acquired in the Merger	43,685
Return on plan assets	4,772
Benefit payments	(600)
Balance at end of year	47,857
Funded status at end of year	13,362
Employee Retirement Plan
Reconciliation of projected benefit obligation:
Projected benefit obligation at beginning of year	26,891	$ 25,405
Interest cost	562	732	$ 901
Actuarial gain	(903)	2,204
Benefit payments	(1,589)	(1,450)
Projected benefit obligation at end of year	24,961	26,891	25,405
Plan assets at fair value (investments in trust funds managed by trustee)
Balance at beginning of year	27,142	25,202
Return on plan assets	3,140	3,390
Benefit payments	(1,589)	(1,450)
Balance at end of year	28,693	27,142	25,202
Funded status at end of year	3,732	251
RETIREMENT PLANS | BMP and Outside Director Retirement Plan
Reconciliation of projected benefit obligation:
Projected benefit obligation at beginning of year	9,328	9,360
Interest cost	12	234	351
Actuarial gain	(277)	505
Benefit payments	(9,063)	(771)
Projected benefit obligation at end of year		9,328	9,360
Plan assets at fair value (investments in trust funds managed by trustee)
Contributions	9,063	771
Benefit payments	(9,063)	(771)
Funded status at end of year		(9,328)
POSTRETIREMENT PLANS
Reconciliation of projected benefit obligation:
Projected benefit obligation at beginning of year	13	1,608
Interest cost		42	56
Actuarial gain		105
Curtailment gain	(1,600)	(1,577)
Benefit payments	(13)	(165)
Projected benefit obligation at end of year		13	$ 1,608
Plan assets at fair value (investments in trust funds managed by trustee)
Contributions	13	165
Benefit payments	$ (13)	(165)
Funded status at end of year		$ (13)