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

The interest on the loan as of the balance sheet date.

No definition available.

Name:	dcom_EmployeeStockOwnershipPlanESOPInterestOnLoan
Namespace Prefix:	dcom_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The number of share allocated to ESOP participants during the period.

No definition available.

Name:	dcom_EsopSharesAllocatedInPeriod
Namespace Prefix:	dcom_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

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

401 (k) plan investments in the holding company's common stock.

No definition available.

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

The maximum loan repayment term.

No definition available.

Name:	dcom_LoanOriginalRepaymentTermMaximum
Namespace Prefix:	dcom_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The amount of the cost recognized during the period for the 401(K) defined contribution plan.

No definition available.

Name:	dcom_PeriodicExpense401kPlan
Namespace Prefix:	dcom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount reported as a liability as of the balance sheet date by the entity (the employer) of the loan made by a third-party lender directly to the ESOP.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Direct Loan
-URI http://asc.fasb.org/extlink&oid=6510849

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 25
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6418455&loc=d3e16545-113920

Name:	us-gaap_EmployeeStockOwnershipPlanESOPDebtStructureDirectLoanAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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.

No definition available.

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

Dividends paid on stock held by an employee stock ownership plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

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

Sum of the allocated, committed-to-be-released and suspense shares of the entity held by the plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

Name:	us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Percentage of vesting of share-based compensation awards.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901