RETIREMENT AND POSTRETIREMENT PLANS - Net periodic benefit (credit) cost for the Employee Retirement Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other	Other
Curtailment loss			$ 1,543
BMP and Outside Director Retirement Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Curtailment loss			(1,500)
Employee Retirement Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	$ 900	$ 622	562
Expected return on assets	(1,521)	(1,949)	(1,846)
Amortization of unrealized loss	572	261	824
Net periodic credit	(49)	(1,066)	(460)
BNB Bank Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	564	807
Interest cost	1,263	793
Expected return on assets	(2,760)	(3,441)
Net periodic credit	$ (933)	$ (1,841)
Retirement Plans | BMP and Outside Director Retirement Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost			12
Curtailment loss			1,543
Net periodic credit			$ 1,555