Name:	dcom_AdvancesFromFederalHomeLoanBanksOvernight
Namespace Prefix:	dcom_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of advances from Federal Home Loan Bank (FHLBank) maturing in the next fiscal year after year one. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

Name:	dcom_FederalHomeLoanBankAdvancesMaturitiesAfterYearOne
Namespace Prefix:	dcom_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Maximum amount of Federal Home Loan Bank (FHLBank) advances to member financial institutions.

No definition available.

Name:	dcom_FederalHomeLoanBankAdvancesMaximum
Namespace Prefix:	dcom_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of federal home loan bank callable advances.

No definition available.

Name:	dcom_FederalHomeLoanBankCallableAdvances
Namespace Prefix:	dcom_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

Name:	us-gaap_DebtDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of Federal Home Loan Bank (FHLBank) advances to member financial institutions.

No definition available.

Name:	us-gaap_FederalHomeLoanBankAdvances
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Interest rate of advances made and reported by Federal Home Loan Bank (FHLBank).

No definition available.