XML 72 R49.htm IDEA: XBRL DOCUMENT
v3.22.4

RETIREMENT AND POSTRETIREMENT PLANS (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2022
Employee Retirement Plan |
Defined Benefit Plan Disclosure [Line Items] |
Schedule of funded status of defined benefit plan | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2022 |  | 2021
Reconciliation of projected benefit obligation: | ​ |  |  | ​ |  |
Projected benefit obligation at beginning of year | ​ | $ | 24,961 | ​ | $ | 26,891
Interest cost | ​ |  | 622 | ​ |  | 562
Actuarial (gain) loss | ​ |  | (5,004) | ​ |  | (903)
Benefit payments | ​ |  | (1,558) | ​ |  | (1,589)
Projected benefit obligation at end of year | ​ |  | 19,021 | ​ |  | 24,961
​ | ​ |  |  | ​ |  |
Plan assets at fair value (investments in trust funds managed by trustee) | ​ |  |  | ​ |  |
Balance at beginning of year | ​ |  | 28,693 | ​ |  | 27,142
Return on plan assets | ​ |  | (4,542) | ​ |  | 3,140
Benefit payments | ​ |  | (1,558) | ​ |  | (1,589)
Balance at end of year | ​ |  | 22,593 | ​ |  | 28,693
Funded status at end of year | ​ | $ | 3,572 | ​ | $ | 3,732
​
Components of net periodic benefit (credit) cost included in other non-interest expense | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) | ​ | 2022 |  | 2021 |  | 2020
Interest cost | ​ | $ | 622 | ​ | $ | 562 | ​ | $ | 732
Expected return on plan assets | ​ |  | (1,949) | ​ |  | (1,846) | ​ |  | (1,713)
Amortization of unrealized loss | ​ |  | 261 | ​ |  | 824 | ​ |  | 914
Net periodic benefit (credit) cost | ​ | $ | (1,066) | ​ | $ | (460) | ​ | $ | (67)
​
Schedule of change in accumulated other comprehensive loss | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2022 |  | 2021
Balance at beginning of period | ​ | $ | (4,097) | ​ | $ | (7,119)
Amortization of unrealized loss | ​ |  | 261 | ​ |  | 825
Gain (loss) recognized during the year | ​ |  | (1,487) | ​ |  | 2,197
Balance at the end of the period | ​ | $ | (5,323) | ​ | $ | (4,097)
Period end component of accumulated other comprehensive loss, net of tax | ​ | $ | 3,649 | ​ | $ | 2,808
​
Schedule of major assumptions utilized to determine the net periodic cost of the Employee Retirement Plan benefit obligations | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | At or for the Year Ended December 31, |
​ |  | 2022 |  | 2021 |  | 2020 |
Discount rate used for net periodic benefit cost |  | 2.55 | % | 2.15 | % | 2.97 | %
Discount rate used to determine benefit obligation at period end |  | 4.90 |  | 2.55 |  | 2.15 | ​
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, |
​ |  | 2022 |  | 2021 |
Asset category |  |  |  |  | ​
Equity securities |  | 51 | % | 54 | %
Debt securities (bond mutual funds) |  | 47 |  | 42 | ​
Cash equivalents |  | 2 |  | 4 | ​
Total |  | 100 | % | 100 | %
​
Summary of fair values of the plan assets | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | 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
​ ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2021
​ | ​ | 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 | ​ | $ | — | ​ | $ | 1,001 | ​ | $ | — | ​ | $ | 1,001
Equities: | ​ |  | ​ | ​ |  | ​ | ​ |  | ​ | ​ |  | ​
U.S. large cap | ​ | ​ | 8,579 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 8,579
U.S. mid cap/small cap | ​ |  | 2,896 | ​ |  | — | ​ |  | — | ​ |  | 2,896
International | ​ |  | 3,560 | ​ |  | — | ​ |  | — | ​ |  | 3,560
Equities blend | ​ |  | 479 | ​ |  | — | ​ |  | — | ​ |  | 479
Fixed income securities: | ​ |  | ​ | ​ |  | ​ | ​ |  | ​ | ​ |  | ​
Corporate | ​ |  | — | ​ |  | 1,288 | ​ |  | — | ​ |  | 1,288
Government | ​ |  | 1,406 | ​ |  | — | ​ |  | — | ​ |  | 1,406
Mortgage-backed | ​ |  | — | ​ |  | 1,858 | ​ |  | — | ​ |  | 1,858
High yield bonds and bond funds | ​ |  | — | ​ |  | 7,626 | ​ |  | — | ​ |  | 7,626
Total Plan Assets | ​ | $ | 16,920 | ​ | $ | 11,773 | ​ | $ | — | ​ | $ | 28,693
​
Schedule of expected benefit payments maturities | ​
​ | ​ | ​ | ​
Year Ended December 31, | ​ | Amount
2023 | ​ | $ | 1,526
2024 | ​ |  | 1,521
2025 | ​ |  | 1,498
2026 | ​ |  | 1,452
2027 | ​ |  | 1,403
2028 to 2032 | ​ |  | 6,674
​
BNB Bank Pension Plan |
Defined Benefit Plan Disclosure [Line Items] |
Schedule of funded status of defined benefit plan | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2022 |  | 2021
Reconciliation of projected benefit obligation: | ​ |  |  | ​ | ​ | ​
Projected benefit obligation at beginning of year | ​ | $ | 34,495 | ​ | $ | —
Acquired in the Merger | ​ | ​ | — | ​ | ​ | 33,897
Service cost | ​ |  | 807 | ​ |  | 893
Interest cost | ​ |  | 793 | ​ |  | 609
Actuarial gain | ​ | ​ | (7,111) | ​ | ​ | (304)
Benefit payments | ​ |  | (1,064) | ​ |  | (600)
Projected benefit obligation at end of year | ​ |  | 27,920 | ​ |  | 34,495
​ | ​ |  |  | ​ |  |
Plan assets at fair value (investments in trust funds managed by trustee) | ​ |  |  | ​ |  |
Balance at beginning of year | ​ |  | 47,857 | ​ |  | —
Acquired in the Merger | ​ | ​ | — | ​ | ​ | 43,685
Return on plan assets | ​ |  | (8,221) | ​ |  | 4,772
Benefit payments | ​ |  | (1,064) | ​ |  | (600)
Balance at end of year | ​ |  | 38,572 | ​ |  | 47,857
Funded status at end of year | ​ | $ | 10,652 | ​ | $ | 13,362
​
Components of net periodic benefit (credit) cost included in other non-interest expense | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) | ​ | 2022 |  | 2021
Service cost | ​ | $ | 807 | ​ | $ | 893
Interest cost | ​ | ​ | 793 | ​ | ​ | 609
Expected return on plan assets | ​ |  | (3,441) | ​ |  | (2,883)
Net periodic benefit credit | ​ | $ | (1,841) | ​ | $ | (1,381)
​
Schedule of change in accumulated other comprehensive loss | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2022 |  | 2021
Balance at beginning of period | ​ | $ | 2,193 | ​ | $ | —
Gain recognized during the year | ​ |  | (2,358) | ​ |  | 2,193
Balance at the end of the period | ​ | $ | (165) | ​ | $ | 2,193
Period end component of accumulated other comprehensive income, net of tax | ​ | $ | 113 | ​ | $ | (1,503)
​
Schedule of major assumptions utilized to determine the net periodic cost of the Employee Retirement Plan benefit obligations | ​
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | At or for the Year Ended December 31, | ​
​ |  | 2022 |  | 2021 | ​
Discount rate used for net periodic benefit cost |  | 2.69 | % | 2.33 | %
Discount rate used to determine benefit obligation at period end |  | 4.98 |  | 2.69 | ​
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, | ​ | ​ | December 31, | ​
​ |  | 2022 |  | ​ | 2021 |
Asset category |  |  |  | ​ |  |
Equity securities |  | 51 | % | ​ | 60 | %
Debt securities (bond mutual funds) |  | 46 |  | ​ | 37 |
Cash equivalents |  | 3 |  | ​ | 3 |
Total |  | 100 | % | ​ | 100 | %
​
Summary of fair values of the plan assets | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | 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 | ​ | $ | — | ​ | $ | 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
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Fair Value Measurements
​ | ​ | at December 31, 2021
​ | ​ | 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 | ​ | $ | — | ​ | $ | 1,581 | ​ | $ | — | ​ | $ | 1,581
Equities: | ​ |  | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. large cap | ​ |  | 13,623 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 13,623
U.S. mid cap/small cap | ​ |  | 5,669 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 5,669
International | ​ |  | 8,332 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 8,332
Equities blend | ​ |  | 900 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 900
Fixed income securities: | ​ |  | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Corporate | ​ |  | — | ​ | ​ | 1,696 | ​ | ​ | — | ​ | ​ | 1,696
Government | ​ |  | 1,700 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 1,700
Mortgage-backed | ​ |  | — | ​ | ​ | 2,549 | ​ | ​ | — | ​ | ​ | 2,549
High yield bonds and bond funds | ​ |  | — | ​ | ​ | 11,807 | ​ | ​ | — | ​ | ​ | 11,807
Total Plan Assets | ​ |  | 30,224 | ​ | $ | 17,633 | ​ | $ | — | ​ | $ | 47,857
​
Schedule of expected benefit payments maturities | ​
​ | ​ | ​ | ​
Year Ended December 31, | ​ | Amount
2023 | ​ | $ | 1,337
2024 | ​ |  | 1,365
2025 | ​ |  | 1,456
2026 | ​ |  | 1,694
2027 | ​ |  | 1,688
2028 to 2032 | ​ |  | 10,505
​
BMP and Outside Director Retirement Plan |
Defined Benefit Plan Disclosure [Line Items] |
Schedule of funded status of defined benefit plan | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2021 |  | 2020
Reconciliation of projected benefit obligation: | ​ |  |  | ​ |  |
Projected benefit obligation at beginning of year | ​ | $ | 9,328 | ​ | $ | 9,360
Interest cost | ​ |  | 12 | ​ |  | 234
Benefit payments | ​ |  | (9,063) | ​ |  | (771)
Actuarial (gain) loss | ​ |  | (277) | ​ |  | 505
Projected benefit obligation at end of year | ​ |  | — | ​ |  | 9,328
Plan assets at fair value: | ​ |  |  | ​ |  |
Balance at beginning of year | ​ |  | — | ​ |  | —
Contributions | ​ |  | 9,063 | ​ |  | 771
Benefit payments | ​ |  | (9,063) | ​ |  | (771)
Balance at end of period | ​ |  | — | ​ |  | —
Funded status at end of year | ​ | $ | — | ​ | $ | (9,328)
​
Components of net periodic benefit (credit) cost included in other non-interest expense | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2021 |  | 2020
Interest cost | ​ | $ | 12 | ​ | $ | 234
Curtailment loss | ​ | ​ | 1,543 | ​ | ​ | —
Amortization of unrealized loss | ​ |  | — | ​ |  | 179
Net periodic benefit cost | ​ | $ | 1,555 | ​ | $ | 413
​
Schedule of change in accumulated other comprehensive loss | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2021 |  | 2020
Balance at beginning of year | ​ | $ | (1,820) | ​ | $ | (1,494)
Amortization of unrealized loss | ​ |  | — | ​ |  | 179
Gain (loss) recognized during the year | ​ |  | 277 | ​ |  | (505)
Curtailment credit | ​ | ​ | 1,543 | ​ | ​ | —
Balance at the end of year | ​ | $ | — | ​ | $ | (1,820)
Period end component of accumulated other comprehensive loss, net of tax | ​ | $ | — | ​ | $ | 1,228
​
Schedule of major assumptions utilized to determine the net periodic cost of the Employee Retirement Plan benefit obligations | ​
​ | ​ | ​ | ​
​ | ​ | At or For the Year Ended December 31,
​ |  | 2020 |
Discount rate used for net periodic benefit cost – BMP |  | 2.60 | %
Discount rate used for net periodic benefit cost – Director Retirement Plan |  | 2.68 |
Discount rate used to determine BMP benefit obligation at year end |  | 1.55 |
Discount rate used to determine Director Retirement Plan benefit obligation at year end |  | 1.69 |
​
POSTRETIREMENT PLANS |
Defined Benefit Plan Disclosure [Line Items] |
Schedule of funded status of defined benefit plan | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | ​ | 2021 |  | ​ | 2020
Reconciliation of projected benefit obligation: | ​ |  |  | ​ |  |
Projected benefit obligation at beginning of year | ​ | $ | 13 | ​ | $ | 1,608
Interest cost | ​ |  | — | ​ |  | 42
Actuarial loss | ​ |  | — | ​ |  | 105
Curtailment gain | ​ | ​ | — | ​ | ​ | (1,577)
Benefit payments | ​ |  | (13) | ​ |  | (165)
Projected benefit obligation at end of year | ​ |  | — | ​ |  | 13
Plan assets at fair value: | ​ |  |  | ​ |  |
Balance at beginning of year | ​ |  | — | ​ |  | —
Contributions | ​ |  | 13 | ​ |  | 165
Benefit payments | ​ |  | (13) | ​ |  | (165)
Balance at end of period | ​ |  | — | ​ |  | —
Funded status at end of year | ​ | $ | — | ​ | $ | (13)
​
Components of net periodic benefit (credit) cost included in other non-interest expense | ​
​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
(In thousands) |  | 2020
Interest cost | ​ | $ | 42
Curtailment gain | ​ | ​ | 1,651
Amortization of unrealized loss | ​ |  | (9)
Net periodic benefit cost | ​ | $ | 1,684
​
Schedule of change in accumulated other comprehensive loss | ​
​ | ​ | ​ | ​
​ | ​ | ​ | Year Ended December 31,
(In thousands) |  | 2020
Balance at beginning of period | ​ | $ | 188
Amortization of unrealized loss | ​ |  | (9)
Recognition of prior service cost | ​ | ​ | (74)
Loss recognized during the year | ​ |  | (105)
Balance at the end of the period | ​ | $ | —
Period end component of accumulated other comprehensive loss, net of tax | ​ | $ | —
​
Schedule of major assumptions utilized to determine the net periodic cost of the Employee Retirement Plan benefit obligations | ​
​ | ​ | ​ | ​
​ | ​ | At or For the Year Ended December 31,
​ |  | 2020 |
Discount rate used for net periodic benefit cost |  | 2.69 | %
Discount rate used to determine benefit obligation at period end |  | 0.29 |

X
- Definition Schedule of change in accumulated other comprehensive loss of defined benefit plan assets. + References No definition available. + Details
Name: | dcom_ScheduleOfDefinedBenefitPlansChangeInAccumulatedOtherComprehensiveLossTableTextBlock
Namespace Prefix: | dcom_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of defined benefit plan asset investment. Includes, but is not limited to, fair value of category of plan asset and its level within fair value hierarchy. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanPlanAssetsCategoryTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of benefit obligation and plan assets of defined benefit plan with accumulated benefit obligation in excess of plan assets. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e2417-114920 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e2417-114920 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI https://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 + Details
Name: | us-gaap_ScheduleOfAccumulatedBenefitObligationsInExcessOfFairValueOfPlanAssetsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans. This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAllocationOfPlanAssetsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of assumption used to determine benefit obligation and net periodic benefit cost of defined benefit plan. Includes, but is not limited to, discount rate, rate of compensation increase, expected long-term rate of return on plan assets and interest crediting rate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAssumptionsUsedTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of benefits expected to be paid by pension plans and/or other employee benefit plans in each of the next five fiscal years and in the aggregate for the five fiscal years thereafter. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfExpectedBenefitPaymentsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfNetBenefitCostsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=dcom_BmpAndOutsideDirectorRetirementPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PostemploymentRetirementBenefitsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |