XML 132 R116.htm IDEA: XBRL DOCUMENT
v3.22.0.1

RETIREMENT AND POSTRETIREMENT PLANS - Major assumptions utilized to determine the net periodic cost of the Employee Retirement Plan (Details) | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Retirement Plans [Member] |  |  |
Defined Benefit Plan, Assumptions Used in Calculations [Abstract] |  |  |
Discount rate used for net periodic benefit cost | 2.69% |  |
Discount rate used to determine benefit obligation at period end | 2.69% |  |
Expected long-term return on plan assets used for net periodic benefit cost | 7.25% |  |
Expected long-term return on plan assets used to determine benefit obligation at period end | 7.25% |  |
Employee Retirement Plan |  |  |
Defined Benefit Plan, Assumptions Used in Calculations [Abstract] |  |  |
Discount rate used for net periodic benefit cost | 2.55% | 2.97% | 4.04%
Discount rate used to determine benefit obligation at period end | 2.55% | 2.15% | 2.97%
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%
RETIREMENT PLANS | Board Member Retirement Plan |  |  |
Defined Benefit Plan, Assumptions Used in Calculations [Abstract] |  |  |
Discount rate used for net periodic benefit cost |  | 2.60% | 3.80%
Discount rate used to determine benefit obligation at period end |  | 1.55% | 2.60%
RETIREMENT PLANS | Outside Director Retirement Plan [Member] |  |  |
Defined Benefit Plan, Assumptions Used in Calculations [Abstract] |  |  |
Discount rate used for net periodic benefit cost |  | 2.68% | 3.84%
Discount rate used to determine benefit obligation at period end |  | 1.69% | 2.68%
POSTRETIREMENT PLANS |  |  |
Defined Benefit Plan, Assumptions Used in Calculations [Abstract] |  |  |
Discount rate used for net periodic benefit cost |  | 2.69% | 3.82%
Discount rate used to determine benefit obligation at period end |  | 0.29% | 2.69%

X
- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine benefit obligation of defined benefit plan. + References No definition available. + Details
Name: | dcom_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationExpectedLongTermRateOfReturnOnPlanAssets
Namespace Prefix: | dcom_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan. + 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)(1) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan. + 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)(1) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + 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)(3) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2919-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanAssumptionsUsedInCalculationsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

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_SupplementalEmployeeRetirementPlanDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanNameAxis=dcom_BoardMemberRetirementPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanNameAxis=dcom_OutsideDirectorRetirementPlanMember
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: |