Number of financing receivables that have been commitments to borrowers with outstanding troubled debt restructurings.

No definition available.

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Period Type:	instant

- Definition

Number of loans modified in a manner that met the criteria of a TDR.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The number of TDR loans that have defaulted within twelve months following modification.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Refers to the number of troubled debt restructurings that are on a non-accrual status in the period.

+ References

No definition available.

+ Details

Name:	dcom_NumberOfTroubledDebtRestructuringsOnNonAccrualStatus
Namespace Prefix:	dcom_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	dcom_TroubledDebtRestructuringOnReceivablesAbstract
Namespace Prefix:	dcom_
Data Type:	xbrli:stringItemType
Balance Type:	na
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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953676-111524

+ Details

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

- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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- Details

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Namespace Prefix:
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- Details

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LOANS RECEIVABLE AND CREDIT QUALITY, Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($) Loan	Jun. 30, 2016 Loan	Jun. 30, 2017 USD ($) Loan	Jun. 30, 2016 Loan	Dec. 31, 2016 USD ($) Loan
Troubled Debt Restructuring on Receivables [Abstract]
Number of TDRs on non-accrual status			0		0
Number of loans modified	0		0
Number of loan commitments to borrowers with outstanding TDRs	0		0		0
TDRs which defaulted within twelve months following the modification	0	0	0	0
Real Estate Loans [Member]
Troubled Debt Restructuring on Receivables [Abstract]
Number of loans			7		7
Balance \| $	$ 8,586		$ 8,586		$ 8,689
Real Estate Loans [Member] \| One- to Four-Family Residential, Including Condominium and Cooperative Apartment [Member]
Troubled Debt Restructuring on Receivables [Abstract]
Number of loans			2		2
Balance \| $	399		$ 399		$ 407
Number of loans modified		1		1
Real Estate Loans [Member] \| Multifamily Residential and Residential Mixed Use [Member]
Troubled Debt Restructuring on Receivables [Abstract]
Number of loans			3		3
Balance \| $	639		$ 639		$ 658
Real Estate Loans [Member] \| Commercial Mixed Use Real Estate [Member]
Troubled Debt Restructuring on Receivables [Abstract]
Number of loans			1		1
Balance \| $	4,218		$ 4,218		$ 4,261
Real Estate Loans [Member] \| Commercial Real Estate [Member]
Troubled Debt Restructuring on Receivables [Abstract]
Number of loans			1		1
Balance \| $	$ 3,330		$ 3,330		$ 3,363