Name:	dcom_AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesWeightedAverageDefaultRate
Namespace Prefix:	dcom_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The amount of escrow balances held for loans serviced for other financial institutions.

No definition available.

Name:	dcom_EscrowBalancesHeldForServicedLoans
Namespace Prefix:	dcom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

This is the principal amount outstanding for mortgage loans serviced for others.

No definition available.

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

Refers to amount of amortization expense to servicing asset at fair value.

No definition available.

Name:	dcom_ServicingAssetAtFairValueAmortizedToExpense
Namespace Prefix:	dcom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

Name:	dcom_ServicingAssetsFairValueAbstract
Namespace Prefix:	dcom_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Discount rate which is used to value residual cash flows generated by financial assets of a securitization, asset-backed financing arrangement, or similar transfer regardless of when the transfer occurred.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=d3e107314-111719

Name:	us-gaap_AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Estimated rate of prepayment of principal on financial assets regardless of when the transfer occurred.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=d3e107314-111719

Name:	us-gaap_AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesPrepaymentSpeed
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

Name:	us-gaap_ServicingAssetAtFairValueAdditions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.