FAIR VALUE OF FINANCIAL INSTRUMENTS, Valuation Techniques (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Asset Valuation Approach Broker Quotation Weighting (in hundredths)	10.00%
Fair Value Asset Valuation Approach Internal Cash Flow Valuation Model Weighting (in hundredths)	45.00%
Fair Value Asset Valuation Approach Independent Cash Flow Valuation Model Weighting (in hundredths)	45.00%
Current Discount Rate Trust Preferred Valuation Minimum Value	4.00%
Current discount rate trust preferred valuation maximum value	10.00%
Current discount trust preferred valuation weighted average rate- Pooled Trust Preferred Held To Maturity Securities [Member]	5.90%
Utilized default rates trust preferred valuation minimum value	0.00%
Utilized default rates trust preferred valuation maximum value	2.70%
Utilized default rates trust preferred valuation weighted average value	0.90%
Fair Value Inputs Standard Default Percentage Over Three Years	1.20%
Estimated Annual Recovery Rate	10.00%dcom_EstimatedAnnualRecoveryRate
Outstanding Principal Balance Of Impaired Loans Measured At Fair Value	$ 4,400	$ 4,400
Impaired Loans Measured at Fair Value Allowance balance	$ 0	$ 0

The cumulative allowance for loan losses associated with impaired loans measured at fair value at period end.

No definition available.

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Period Type:	instant

- Definition

Maximum value of the current discount rates utilized in the valuation of the trust preferred securities.

+ References

No definition available.

+ Details

Name:	dcom_CurrentDiscountRateTrustPreferredValuationMaximumValue
Namespace Prefix:	dcom_
Data Type:	num:percentItemType
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Period Type:	instant

- Definition

Minimum value of the current discount rates utilized in the valuation of the trust preferred securities.

+ References

No definition available.

+ Details

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

- Definition

The weighted average current discount rate utlized in the internal cash flow model valuation of trust preferred securities.

+ References

No definition available.

+ Details

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

- Definition

The estimated annual recovery rate utilized in the Internal Cash Flow Valuation model of trust preferred securities at period end.

+ References

No definition available.

+ Details

Name:	dcom_EstimatedAnnualRecoveryRate
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The valuation approach for assessing fair value on held-to-maturity investments that relied on broker quotations under the criteria of distressed sale pricing.

+ References

No definition available.

+ Details

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

- Definition

The valuation approach for assessing fair value on held-to-maturity investments that relied on a minimum of two of three independent cash flow models.

+ References

No definition available.

+ Details

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

- Definition

The valuation approach for assessing fair value on held-to-maturity investments that relied on internally created cash flow model.

+ References

No definition available.

+ Details

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

- Definition

Description of the standard default rate applied by entity to assess the value of the assets underlying the investment.

+ References

No definition available.

+ Details

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

- Definition

The principal balance outstanding as of the date indicated on impaired loans that are measured at fair value.

+ References

No definition available.

+ Details

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

- Definition

The maximum value of the utilized default rates in the internal cash floe model valuation of trust preferred securities at period end

+ References

No definition available.

+ Details

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

- Definition

The minimum value of the utilized default rates in the internal cash floe model valuation of trust preferred securities at period end

+ References

No definition available.

+ Details

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

- Definition

The minimum value of the utilized default rates in the internal cash floe model valuation of trust preferred securities at period end

+ References

No definition available.

+ Details

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

- Details

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