XML 38 R40.htm IDEA: XBRL DOCUMENT v2.4.1.9
ALLOWANCE FOR LOAN LOSSES AND RESERVE FOR FIRST LOSS POSITION ON MULTIFAMILY LOANS SOLD TO FNMA (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]      
Allowance for Loan Losses at Period End on Substandard Non Impaired Loans $ 122dcom_AllowanceForLoanLossesAtPeriodEndOnSubstandardNonImpairedLoans   $ 371dcom_AllowanceForLoanLossesAtPeriodEndOnSubstandardNonImpairedLoans
Increase (Decrease) in the balance of Substandard non-impaired loans (5,370)dcom_IncreaseDecreaseInBalanceOfSubstandardNonImpairedLoans    
Financing Receivable Special Mention Allowance For Loan Losses period end balance 170dcom_FinancingReceivableSpecialMentionAllowanceForLoanLosses   228dcom_FinancingReceivableSpecialMentionAllowanceForLoanLosses
Financing Receivable Special Mention Balance Increase (Decrease) (3,672)dcom_FinancingReceivableSpecialMentionIncrease    
Reserve Liability On The First Loss Position [Roll Forward]      
Liability for First Loss Position Extinguished 0dcom_CreditProvisionToFirstLossPosition 1,040dcom_CreditProvisionToFirstLossPosition  
One To Four Family Residential And Cooperative Unit Allowance [Member]      
Financing Receivable, Allowance for Credit Losses [Roll Forward]      
Beginning balance 150us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
236us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
 
Provision (credit) for loan losses 61us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
49us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
 
Charge-offs (102)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
(9)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
 
Recoveries 2us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
1us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
 
Ending balance 111us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
277us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
 
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]      
Ending balance - loans individually evaluated for impairment 603us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
  605us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
Ending balance - loans collectively evaluated for impairment 70,379us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
  72,895us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
Allowance balance associated with loans individually evaluated for impairment 0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
  0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
Allowance balance associated with loans collectivelly evaluated for impairment 111us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
  150us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance 643us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
  646us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
  0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Recorded Investment 603us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
[1]   605us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
[1]
Impaired Financing Receivable, with Related Allowance, Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
[1]   0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
[1]
Impaired Financing Receivables With No Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
  0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
Impaired Financing Receivables With Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
  0dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment 604us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
959us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
 
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
106us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
 
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method 12us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
15us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
 
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
 
Multifamily Residential And Residential Mixed Use Allowance [Member]      
Financing Receivable, Allowance for Credit Losses [Roll Forward]      
Beginning balance 13,852us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
13,840us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
 
Provision (credit) for loan losses 322us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
338us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
 
Charge-offs (1)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
(37)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
 
Recoveries 0us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
170us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
 
Ending balance 14,173us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
14,311us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
 
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]      
Ending balance - loans individually evaluated for impairment 1,259us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
  1,272us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
Ending balance - loans collectively evaluated for impairment 3,397,273us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
  3,297,176us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
Allowance balance associated with loans individually evaluated for impairment 0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
  0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
Allowance balance associated with loans collectivelly evaluated for impairment 14,173us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
  13,852us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance 1,259us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
  1,272us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
  0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Recorded Investment 1,259us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
[1]   1,272us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
[1]
Impaired Financing Receivable, with Related Allowance, Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
[1]   0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
[1]
Impaired Financing Receivables With No Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
  0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
Impaired Financing Receivables With Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
  0dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment 1,265us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
2,377us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
 
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
 
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method 15us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
22us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
 
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
 
Commercial Mixed Use Real Estate Allowance [Member]      
Financing Receivable, Allowance for Credit Losses [Roll Forward]      
Beginning balance 1,644us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
3,003us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
 
Provision (credit) for loan losses (60)us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
(206)us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
 
Charge-offs (37)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
(30)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
 
Recoveries 19us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
0us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
 
Ending balance 1,566us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
2,767us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
 
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]      
Ending balance - loans individually evaluated for impairment 4,400us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
  4,400us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
Ending balance - loans collectively evaluated for impairment 331,017us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
  324,267us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
Allowance balance associated with loans individually evaluated for impairment 0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
  0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
Allowance balance associated with loans collectivelly evaluated for impairment 1,566us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
  1,644us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance 4,405us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
  4,425us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
  0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Recorded Investment 4,400us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
[1]   4,400us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
[1]
Impaired Financing Receivable, with Related Allowance, Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
[1]   0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
[1]
Impaired Financing Receivables With No Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
  0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
Impaired Financing Receivables With Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
  0dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment 4,400us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
 
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
4,400us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
 
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method 44us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
 
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_MixedUseCommercialRealEstateAllowanceMember
 
Commercial Real Estate [Member]      
Financing Receivable, Allowance for Credit Losses [Roll Forward]      
Beginning balance 2,823us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
3,047us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
 
Provision (credit) for loan losses (494)us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
102us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
 
Charge-offs 0us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
(108)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
 
Recoveries 36us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
7us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
 
Ending balance 2,365us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
3,048us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
 
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]      
Ending balance - loans individually evaluated for impairment 8,191us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
  13,707us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
Ending balance - loans collectively evaluated for impairment 419,983us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
  403,089us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
Allowance balance associated with loans individually evaluated for impairment 0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
  19us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
Allowance balance associated with loans collectivelly evaluated for impairment 2,365us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
  2,804us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance 10,289us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
  10,306us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
  5,500us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Recorded Investment 8,191us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
[1]   8,207us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
[1]
Impaired Financing Receivable, with Related Allowance, Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
[1]   5,500us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
[1]
Impaired Financing Receivables With No Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
  0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
Impaired Financing Receivables With Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
  19dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment 8,199us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
7,198us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
 
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment 2,750us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
15,006us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
 
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method 36us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
185us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
 
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method 97us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
31us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_CommercialRealEstateAllowanceMember
 
Construction Loan Receivable [Member]      
Financing Receivable, Allowance for Credit Losses [Roll Forward]      
Beginning balance 0us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
3us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
 
Provision (credit) for loan losses 0us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
(2)us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
 
Charge-offs 0us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
0us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
 
Recoveries 0us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
0us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
 
Ending balance 0us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
1us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
 
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]      
Ending balance - loans individually evaluated for impairment 0us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
  0us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
Ending balance - loans collectively evaluated for impairment 0us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
  0us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
Allowance balance associated with loans individually evaluated for impairment 0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
  0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
Allowance balance associated with loans collectivelly evaluated for impairment 0us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
  0us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance 0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
  0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
  0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
[1]   0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
[1]
Impaired Financing Receivable, with Related Allowance, Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
[1]   0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
[1]
Impaired Financing Receivables With No Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
  0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
Impaired Financing Receivables With Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
  0dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
 
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
 
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method 0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
 
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConstructionLoanReceivableAllowanceMember
 
Total Real Estate Loans [Member]      
Financing Receivable, Allowance for Credit Losses [Roll Forward]      
Beginning balance 18,469us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
20,129us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
 
Provision (credit) for loan losses (171)us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
281us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
 
Charge-offs (140)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
(184)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
 
Recoveries 57us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
178us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
 
Ending balance 18,215us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
20,404us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
 
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]      
Ending balance - loans individually evaluated for impairment 14,453us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
  19,984us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
Ending balance - loans collectively evaluated for impairment 4,218,652us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
  4,097,427us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
Allowance balance associated with loans individually evaluated for impairment 0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
  19us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
Allowance balance associated with loans collectivelly evaluated for impairment 18,215us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
  18,450us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance 16,596us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
  16,649us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
  5,500us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
Impaired Financing Receivable, with No Related Allowance, Recorded Investment 14,453us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
[1]   14,484us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
[1]
Impaired Financing Receivable, with Related Allowance, Recorded Investment 0us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
[1]   5,500us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
[1]
Impaired Financing Receivables With No Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
  0dcom_ImpairedFinancingReceivablesAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
Impaired Financing Receivables With Allocated Reserves Within Allowance For Loan Losses Recognized For Impaired Receivables 0dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
  19dcom_ImpairedFinancingReceivablesWithAllocatedReservesWithinAllowanceForLoanLossesRecognizedForImpairedReceivables
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment 14,468us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
10,534us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
 
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment 2,750us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
19,512us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
 
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method 107us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
222us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
 
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method 97us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
31us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_TotalRealEstateAndLoansHeldForSaleReceivableMember
 
Consumer Loan [Member]      
Financing Receivable, Allowance for Credit Losses [Roll Forward]      
Beginning balance 24us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
24us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
 
Provision (credit) for loan losses (1)us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
1us-gaap_ProvisionForLoanLeaseAndOtherLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
 
Charge-offs (1)us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
0us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
 
Recoveries 0us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
0us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
 
Ending balance 22us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
25us-gaap_FinancingReceivableAllowanceForCreditLosses
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
 
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]      
Ending balance - loans individually evaluated for impairment 0us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
  0us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
Ending balance - loans collectively evaluated for impairment 1,612us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
  1,829us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
Allowance balance associated with loans individually evaluated for impairment 0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
  0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
Allowance balance associated with loans collectivelly evaluated for impairment $ 22us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
  $ 24us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= dcom_ConsumerLoanAllowanceMember
[1] The recorded investment excludes accrued interest receivable and loan origination fees, net, due to immateriality.