RETIREMENT AND POSTRETIREMENT PLANS - Funded status of the Employee Retirement Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Employee Retirement Plan
Reconciliation of projected benefit obligation:
Projected benefit obligation at beginning of year	$ 19,021	$ 24,961
Interest cost	900	622	$ 562
Actuarial (gain) loss	384	(5,004)
Benefit payments	(1,584)	(1,558)
Projected benefit obligation at end of year	18,721	19,021	24,961
Plan assets at fair value (investments in trust funds managed by trustee)
Balance at beginning of year	22,593	28,693
Return on plan assets	294	(4,542)
Benefit payments	(1,584)	(1,558)
Balance at end of year	21,303	22,593	28,693
Funded status at end of year	2,582	3,572
BNB Bank Pension Plan
Reconciliation of projected benefit obligation:
Projected benefit obligation at beginning of year	27,920	34,495
Service cost	564	807
Interest cost	1,263	793
Actuarial (gain) loss	(883)	(7,111)
Curtailment	(446)
Benefit payments	(1,136)	(1,064)
Projected benefit obligation at end of year	27,282	27,920	34,495
Plan assets at fair value (investments in trust funds managed by trustee)
Balance at beginning of year	38,572	47,857
Return on plan assets	734	(8,221)
Benefit payments	(1,136)	(1,064)
Balance at end of year	38,170	38,572	47,857
Funded status at end of year	$ 10,888	$ 10,652
Retirement Plans | BMP and Outside Director Retirement Plan
Reconciliation of projected benefit obligation:
Projected benefit obligation at beginning of year			9,328
Interest cost			12
Actuarial (gain) loss			(277)
Benefit payments			(9,063)
Plan assets at fair value (investments in trust funds managed by trustee)
Contributions			9,063
Benefit payments			(9,063)
Postretirement Benefit Plan
Reconciliation of projected benefit obligation:
Projected benefit obligation at beginning of year			13
Benefit payments			(13)
Plan assets at fair value (investments in trust funds managed by trustee)
Contributions			13
Benefit payments			$ (13)