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RETIREMENT AND POSTRETIREMENT PLANS (Tables) | 12 Months Ended
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Dec. 31, 2023
Employee Retirement Plan |
Defined Benefit Plan Disclosure [Line Items] |
Schedule of funded status of defined benefit plan | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2023 |  | 2022
Reconciliation of projected benefit obligation: | ​ |  |  | ​ |  |
Projected benefit obligation at beginning of year | ​ | $ | 19,021 | ​ | $ | 24,961
Interest cost | ​ |  | 900 | ​ |  | 622
Actuarial (gain) loss | ​ |  | 384 | ​ |  | (5,004)
Benefit payments | ​ |  | (1,584) | ​ |  | (1,558)
Projected benefit obligation at end of year | ​ |  | 18,721 | ​ |  | 19,021
​ | ​ |  |  | ​ |  |
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
Funded status at end of year | ​ | $ | 2,582 | ​ | $ | 3,572
Schedule of components of net periodic benefit (credit) cost included in other non-interest expense | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) | ​ | 2023 |  | 2022 |  | 2021
Interest cost | ​ | $ | 900 | ​ | $ | 622 | ​ | $ | 562
Expected return on plan assets | ​ |  | (1,521) | ​ |  | (1,949) | ​ |  | (1,846)
Amortization of unrealized loss | ​ |  | 572 | ​ |  | 261 | ​ |  | 824
Net periodic benefit (credit) cost | ​ | $ | (49) | ​ | $ | (1,066) | ​ | $ | (460)
Schedule of change in accumulated other comprehensive loss | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2023 |  | 2022
Balance at beginning of period | ​ | $ | (5,323) | ​ | $ | (4,097)
Amortization of unrealized loss | ​ |  | 572 | ​ |  | 261
Loss recognized during the year | ​ |  | (1,612) | ​ |  | (1,487)
Balance at the end of the period | ​ | $ | (6,363) | ​ | $ | (5,323)
Period end component of accumulated other comprehensive loss, net of tax | ​ | $ | 4,343 | ​ | $ | 3,649
Schedule of major assumptions utilized to determine the net periodic cost of Plan benefit obligations | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | At or for the Year Ended December 31, | ​
​ |  | 2023 | ​ | ​ | 2022 | ​ | ​ | 2021 | ​
Discount rate used for net periodic benefit cost |  | 4.90 | % | ​ | 2.55 | % | ​ | 2.15 | %
Discount rate used to determine benefit obligation at period end |  | 4.70 |  | ​ | 4.90 |  | ​ | 2.55 | ​
Expected long-term return on plan assets used for net periodic benefit cost |  | 7.00 |  | ​ | 7.00 |  | ​ | 7.00 | ​
Expected long-term return on plan assets used to determine benefit obligation at period end |  | 7.00 |  | ​ | 7.00 |  | ​ | 7.00 | ​
Summary of plan asset allocation by asset category | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, | ​
​ |  | 2023 | ​ | ​ | 2022 | ​
Asset category: |  |  |  | ​ |  | ​
Equity securities |  | — | % | ​ | 51 | %
Debt securities |  | 100 |  | ​ | 47 | ​
Cash equivalents |  | — |  | ​ | 2 | ​
Total |  | 100 | % | ​ | 100 | %
Summary of fair values of the plan assets | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2023
​ | ​ | Fair Value Measurements Using:
​ | ​ | Quoted | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Prices in | ​ | Significant | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Active Markets for | ​ | Other | ​ | Significant | ​ | ​ | ​
​ | ​ | Identical | ​ | Observable | ​ | Unobservable | ​ | ​ | ​
(In thousands) |  | Assets (Level 1) |  | Inputs (Level 2) |  | Inputs (Level 3) |  | Total
Description: | ​ |  | ​ | ​ | ​ | ​ | ​ |  | ​ | ​ |  | ​
Cash and cash equivalents | ​ | $ | — | ​ | $ | 58 | ​ | $ | — | ​ | $ | 58
Fixed income securities: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Government | ​ | ​ | 21,245 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 21,245
Total Plan Assets | ​ | $ | 21,245 | ​ | $ | 58 | ​ | $ | — | ​ | $ | 21,303
​ ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2022
​ | ​ | Fair Value Measurements Using:
​ | ​ | Quoted | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Prices in | ​ | Significant | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Active Markets for | ​ | Other | ​ | Significant | ​ | ​ | ​
​ | ​ | Identical | ​ | Observable | ​ | Unobservable | ​ | ​ | ​
(In thousands) |  | Assets (Level 1) |  | Inputs (Level 2) |  | Inputs (Level 3) |  | Total
Description: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Cash and cash equivalents | ​ | $ | — | ​ | $ | 541 | ​ | $ | — | ​ | $ | 541
Equities: | ​ |  | ​ | ​ |  | ​ | ​ |  | ​ | ​ |  | ​
U.S. large cap | ​ | ​ | 8,398 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 8,398
U.S. mid cap/small cap | ​ |  | 2,348 | ​ |  | — | ​ |  | — | ​ |  | 2,348
International | ​ |  | 2,718 | ​ |  | — | ​ |  | — | ​ |  | 2,718
Equities blend | ​ |  | 192 | ​ |  | — | ​ |  | — | ​ |  | 192
Fixed income securities: | ​ |  | ​ | ​ |  | ​ | ​ |  | ​ | ​ |  | ​
Corporate | ​ |  | — | ​ |  | 1,305 | ​ |  | — | ​ |  | 1,305
Government | ​ |  | 2,527 | ​ |  | — | ​ |  | — | ​ |  | 2,527
Mortgage-backed | ​ |  | — | ​ |  | 586 | ​ |  | — | ​ |  | 586
High yield bonds and bond funds | ​ |  | — | ​ |  | 3,978 | ​ |  | — | ​ |  | 3,978
Total Plan Assets | ​ | $ | 16,183 | ​ | $ | 6,410 | ​ | $ | — | ​ | $ | 22,593
Schedule of expected benefit payments maturities | ​
​ | ​ | ​ | ​
(In thousands) | ​ | ​
2024 | ​ | $ | 1,526
2025 | ​ |  | 1,518
2026 | ​ |  | 1,475
2027 | ​ |  | 1,447
2028 | ​ |  | 1,401
2029 to 2033 | ​ |  | 6,621
BNB Bank Pension Plan |
Defined Benefit Plan Disclosure [Line Items] |
Schedule of funded status of defined benefit plan | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2023 |  | 2022
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 | ​ | ​ | (883) | ​ | ​ | (7,111)
Curtailment | ​ | ​ | (446) | ​ | ​ | —
Benefit payments | ​ |  | (1,136) | ​ |  | (1,064)
Projected benefit obligation at end of year | ​ |  | 27,282 | ​ |  | 27,920
​ | ​ |  |  | ​ |  |
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
Funded status at end of year | ​ | $ | 10,888 | ​ | $ | 10,652
Schedule of components of net periodic benefit (credit) cost included in other non-interest expense | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) | ​ | 2023 |  | 2022
Service cost | ​ | $ | 564 | ​ | $ | 807
Interest cost | ​ | ​ | 1,263 | ​ | ​ | 793
Expected return on plan assets | ​ |  | (2,760) | ​ |  | (3,441)
Net periodic benefit credit | ​ | $ | (933) | ​ | $ | (1,841)
Schedule of change in accumulated other comprehensive loss | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2023 |  | 2022
Balance at beginning of period | ​ | $ | (2,358) | ​ | $ | 2,193
Loss recognized during the year | ​ |  | (698) | ​ |  | (4,551)
Balance at the end of the period | ​ | $ | (3,056) | ​ | $ | (2,358)
Period end component of accumulated other comprehensive income, net of tax | ​ | $ | 2,087 | ​ | $ | 1,617
Schedule of major assumptions utilized to determine the net periodic cost of Plan benefit obligations | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | At or for the Year Ended December 31,
​ |  | 2023 | ​ | ​ | 2022 | ​
Discount rate used for net periodic benefit cost |  | 4.98 | % | ​ | 2.69 | %
Discount rate used to determine benefit obligation at period end |  | 4.79 |  | ​ | 4.98 | ​
Expected long-term return on plan assets used for net periodic benefit cost |  | 7.25 |  | ​ | 7.25 | ​
Expected long-term return on plan assets used to determine benefit obligation at period end |  | 7.25 |  | ​ | 7.25 | ​
Summary of plan asset allocation by asset category | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, | ​
​ |  | 2023 | ​ | ​ | 2022 | ​
Asset category: |  |  |  | ​ |  |
Equity securities |  | - | % | ​ | 51 | %
Debt securities |  | 99 |  | ​ | 46 |
Cash equivalents |  | 1 |  | ​ | 3 |
Total |  | 100 | % | ​ | 100 | %
Summary of fair values of the plan assets | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Fair Value Measurements
​ | ​ | at December 31, 2023
​ | ​ | Quoted | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Prices in | ​ | Significant | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Active Markets for | ​ | Other | ​ | Significant | ​ | ​ | ​
​ | ​ | Identical | ​ | Observable | ​ | Unobservable | ​ | ​ | ​
(In thousands) |  | Assets (Level 1) |  | Inputs (Level 2) |  | Inputs (Level 3) |  | Total
Description: | ​ |  | ​ | ​ | ​ | ​ | ​ |  | ​ | ​ |  | ​
Cash and cash equivalents | ​ | $ | — | ​ | $ | 317 | ​ | $ | — | ​ | $ | 317
Fixed income securities: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Government | ​ | ​ | 37,853 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 37,853
Total Plan Assets | ​ | $ | 37,853 | ​ | $ | 317 | ​ | $ | — | ​ | $ | 38,170
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Fair Value Measurements
​ | ​ | at December 31, 2022
​ | ​ | Quoted | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Prices in | ​ | Significant | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Active Markets for | ​ | Other | ​ | Significant | ​ | ​ | ​
​ | ​ | Identical | ​ | Observable | ​ | Unobservable | ​ | ​ | ​
(In thousands) |  | Assets (Level 1) |  | Inputs (Level 2) |  | Inputs (Level 3) |  | Total
Description: | ​ |  | ​ | ​ |  | ​ | ​ |  | ​ | ​ |  | ​
Cash and cash equivalents | ​ | $ | — | ​ | $ | 1,001 | ​ | $ | — | ​ | $ | 1,001
Equities: | ​ |  | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. large cap | ​ |  | 14,310 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 14,310
U.S. mid cap/small cap | ​ |  | 4,094 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 4,094
International | ​ |  | 4,658 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 4,658
Equities blend | ​ |  | 308 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 308
Fixed income securities: | ​ |  | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Corporate | ​ |  | — | ​ | ​ | 2,203 | ​ | ​ | — | ​ | ​ | 2,203
Government | ​ |  | 4,275 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 4,275
Mortgage-backed | ​ |  | — | ​ | ​ | 979 | ​ | ​ | — | ​ | ​ | 979
High yield bonds and bond funds | ​ |  | — | ​ | ​ | 6,744 | ​ | ​ | — | ​ | ​ | 6,744
Total Plan Assets | ​ | $ | 27,645 | ​ | $ | 10,927 | ​ | $ | — | ​ | $ | 38,572
Schedule of expected benefit payments maturities | ​
​ | ​ | ​ | ​
(In thousands) | ​ | ​
2024 | ​ | $ | 1,298
2025 | ​ |  | 1,379
2026 | ​ |  | 1,501
2027 | ​ |  | 1,477
2028 | ​ |  | 1,529
2029 to 2033 | ​ |  | 9,075
BMP and Outside Director Retirement Plan |
Defined Benefit Plan Disclosure [Line Items] |
Schedule of funded status of defined benefit plan | ​
​ | ​ | ​ | ​
​ | ​ | Year Ended
(In thousands) |  | December 31, 2021
Reconciliation of projected benefit obligation: | ​ |  |
Projected benefit obligation at beginning of year | ​ | $ | 9,328
Interest cost | ​ |  | 12
Benefit payments | ​ |  | (9,063)
Actuarial (gain) loss | ​ |  | (277)
Projected benefit obligation at end of year | ​ |  | —
Plan assets at fair value: | ​ |  |
Balance at beginning of year | ​ |  | —
Contributions | ​ |  | 9,063
Benefit payments | ​ |  | (9,063)
Balance at end of period | ​ |  | —
Funded status at end of year | ​ | $ | —
Schedule of components of net periodic benefit (credit) cost included in other non-interest expense | ​
​ | ​ | ​ | ​
​ | ​ | Year Ended
(In thousands) |  | December 31, 2021
Interest cost | ​ | $ | 12
Curtailment loss | ​ | ​ | 1,543
Amortization of unrealized loss | ​ |  | —
Net periodic benefit cost | ​ | $ | 1,555
Schedule of change in accumulated other comprehensive loss | ​
​ | ​ | ​ | ​
​ | ​ | Year Ended
(In thousands) |  | December 31, 2021
Balance at beginning of year | ​ | $ | (1,820)
Amortization of unrealized loss | ​ |  | —
Gain (loss) recognized during the year | ​ |  | 277
Curtailment credit | ​ | ​ | 1,543
Balance at the end of year | ​ | $ | —
Period end component of accumulated other comprehensive loss, net of tax | ​ | $ | —
POSTRETIREMENT PLANS |
Defined Benefit Plan Disclosure [Line Items] |
Schedule of funded status of defined benefit plan | ​
​ | ​ | ​ | ​
​ | ​ | Year Ended
(In thousands) |  | December 31, 2021
Reconciliation of projected benefit obligation: | ​ |  |
Projected benefit obligation at beginning of year | ​ | $ | 13
Interest cost | ​ |  | —
Actuarial loss | ​ |  | —
Curtailment gain | ​ | ​ | —
Benefit payments | ​ |  | (13)
Projected benefit obligation at end of year | ​ |  | —
Plan assets at fair value: | ​ |  |
Balance at beginning of year | ​ |  | —
Contributions | ​ |  | 13
Benefit payments | ​ |  | (13)
Balance at end of period | ​ |  | —
Funded status at end of year | ​ | $ | —

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