Financing Receivable, Modifications, Number of Contracts

No definition available.

Name:	dnbf_FinancingReceivableModificationsNumberOfContracts3
Namespace Prefix:	dnbf_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Financing Receivable Modifications Recorded Investment Additions (Reductions)

+ References

No definition available.

+ Details

Name:	dnbf_FinancingReceivableModificationsRecordedInvestmentAdditionsReductions
Namespace Prefix:	dnbf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Monthly Payment Period, Reduced Period

+ References

No definition available.

+ Details

Name:	dnbf_MonthlyPaymentPeriodReducedPeriod
Namespace Prefix:	dnbf_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

Post-modification amount of investment in financing receivables 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=35738203&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

+ Details

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 34

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivableTroubledDebtRestructuringAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableTroubledDebtRestructuringAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Allowance For Credit Losses (Narrative) (Details)	3 Months Ended		9 Months Ended
Allowance For Credit Losses (Narrative) (Details)	Sep. 30, 2015 USD ($) loan	Sep. 30, 2014 USD ($) loan	Sep. 30, 2015 USD ($) loan	Sep. 30, 2014 USD ($) loan	Dec. 31, 2014 USD ($) loan
Commercial Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Number of TDRs \| loan		1		1	1
TDR amount		$ 2,269,000		$ 2,269,000	$ 2,246,000
Reduction of principal			$ 0
Pre-modification recorded investment			2,272,000
Post-modification recorded investment			$ 2,272,000
Number of subsequent defaults \| loan	0	0	0	0
Consumer: Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of TDRs \| loan	1	1	1	1	1
TDR amount	$ 102,000	$ 102,000	$ 102,000	$ 102,000	$ 102,000
Monthly payment reduced period, in months			36 months
Reduction of principal			$ 0
Pre-modification recorded investment			102,000
Post-modification recorded investment			$ 102,000
Number of subsequent defaults \| loan	0	0	0	0