EMPLOYEE BENEFIT PLANS, ESOP PLAN (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jun. 26, 1996
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Interest on loan (in hundredths)	8.00%	8.00%
ESOP [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
ESOP loan amount	$ 3,567	$ 3,721		$ 11,638
Shares Contributed to ESOP				3,927,825
Loan original repayment term, Maximum				10 years
Amended loan repayment term	30 years
ESOP Shares allocated in period	78,155	78,155	78,155
Employee Stock Ownership Plan (ESOP), Compensation Expense Gross Amount	1,691	1,640	1,700
Dividends paid to ESOP	$ 613	$ 656	$ 700

The amended loan repayment term.

No definition available.

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- Definition

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

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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Period Type:	instant

- Definition

The gross amount of ESOP plan compensation cost recognized during the period which exceeds the amount recognized in the statement of cash flows by adjustments related to dividends and forfeitures.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

The maximum loan repayment term.

+ References

No definition available.

+ Details

Name:	dcom_LoanOriginalRepaymentTermMaximum
Namespace Prefix:	dcom_
Data Type:	xbrli:durationItemType
Balance Type:	na
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- Definition

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.

+ References

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

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 93-6

-Paragraph 24, 25

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 93-6

-Paragraph 53

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

- Definition

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

+ References

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 93-6

-Paragraph 53

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant