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Investment Securities (Unrealized Losses And Fair Value) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Securities [Line Items]    
Held-to-maturity Securities, Fair Value, Total $ 17,776us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue $ 22,097us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue
Held-to-maturity Securities, Unrealized Losses (386)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAggregateLoss2 (576)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAggregateLoss2
Held-to-maturity Securities, Fair Value Impaired Less Than 12 Months 6,111us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue 5,181us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Held-to-maturity Securities, Unrealized Loss Less Than 12 Months (42)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateAccumulatedLoss (36)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateAccumulatedLoss
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value 11,665us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue 16,916us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses (344)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateAccumulatedLoss (540)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateAccumulatedLoss
Available-for-sale Securities, Fair Value, Total 35,225us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue 112,713us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
Available-for-sale Securities, Unrealized Loss, Total (528)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci (955)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
Available-for-sale Securities, Fair Value Impaired Less Than 12 Months 14,902us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue 79,778us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Available-for-sale Securities, Unrealized Loss Less Than 12 Months (90)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLossesAccumulatedInAoci (180)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLossesAccumulatedInAoci
Available-for-sale Securities, Fair Value Impaired More Than 12 Months 20,323us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue 32,935us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Available-for-sale Securities, Unrealized Loss More Than 12 Months (438)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci (775)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
US Government Agency Obligations [Member]    
Securities [Line Items]    
Available-for-sale Securities, Fair Value, Total 5,007us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
56,342us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Available-for-sale Securities, Unrealized Loss, Total (47)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
(197)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Available-for-sale Securities, Fair Value Impaired Less Than 12 Months 5,007us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
49,222us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Available-for-sale Securities, Unrealized Loss Less Than 12 Months (47)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
(97)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Available-for-sale Securities, Fair Value Impaired More Than 12 Months   7,120us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Available-for-sale Securities, Unrealized Loss More Than 12 Months   (100)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Government Sponsored Entities (GSE) Mortgage-Backed Securities [Member]    
Securities [Line Items]    
Available-for-sale Securities, Fair Value, Total 6,952us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
22,157us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Securities, Unrealized Loss, Total (63)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
(135)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Securities, Fair Value Impaired Less Than 12 Months 2,092us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
14,996us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Securities, Unrealized Loss Less Than 12 Months (7)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
(38)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Securities, Fair Value Impaired More Than 12 Months 4,860us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
7,161us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Securities, Unrealized Loss More Than 12 Months (56)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
(97)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Collateralized Mortgage Obligations GSE [Member]    
Securities [Line Items]    
Available-for-sale Securities, Fair Value, Total 13,009us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
18,133us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
Available-for-sale Securities, Unrealized Loss, Total (313)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
(496)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
Available-for-sale Securities, Fair Value Impaired Less Than 12 Months   3,669us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
Available-for-sale Securities, Unrealized Loss Less Than 12 Months   (5)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
Available-for-sale Securities, Fair Value Impaired More Than 12 Months 13,009us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
14,464us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
Available-for-sale Securities, Unrealized Loss More Than 12 Months (313)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
(491)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
Corporate Bonds [Member]    
Securities [Line Items]    
Available-for-sale Securities, Fair Value, Total 10,245us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
13,102us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Available-for-sale Securities, Unrealized Loss, Total (94)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
(106)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Available-for-sale Securities, Fair Value Impaired Less Than 12 Months 7,803us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
9,531us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Available-for-sale Securities, Unrealized Loss Less Than 12 Months (36)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
(31)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Available-for-sale Securities, Fair Value Impaired More Than 12 Months 2,442us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
3,571us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Available-for-sale Securities, Unrealized Loss More Than 12 Months (58)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
(75)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
State And Municipal Tax-Exempt [Member]    
Securities [Line Items]    
Available-for-sale Securities, Fair Value, Total   2,967us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Available-for-sale Securities, Unrealized Loss, Total   (10)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Available-for-sale Securities, Fair Value Impaired Less Than 12 Months   2,360us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Available-for-sale Securities, Unrealized Loss Less Than 12 Months   (9)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Available-for-sale Securities, Fair Value Impaired More Than 12 Months   607us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Available-for-sale Securities, Unrealized Loss More Than 12 Months   (1)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Equity Securities [Member]    
Securities [Line Items]    
Available-for-sale Securities, Fair Value, Total 12us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
12us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Available-for-sale Securities, Unrealized Loss, Total (11)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
(11)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Available-for-sale Securities, Fair Value Impaired More Than 12 Months 12us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
12us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Available-for-sale Securities, Unrealized Loss More Than 12 Months (11)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
(11)dnbf_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossesAccumulatedInAoci
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Collateralized Mortgage Obligations GSE [Member]    
Securities [Line Items]    
Held-to-maturity Securities, Fair Value, Total 1,412us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
3,043us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Held-to-maturity Securities, Unrealized Losses (6)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
(29)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Held-to-maturity Securities, Fair Value Impaired Less Than 12 Months   3,043us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Held-to-maturity Securities, Unrealized Loss Less Than 12 Months   (29)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateAccumulatedLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value 1,412us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
 
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses (6)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateAccumulatedLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
 
State And Municipal Tax-Exempt [Member]    
Securities [Line Items]    
Held-to-maturity Securities, Fair Value, Total 16,364us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
19,054us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity Securities, Unrealized Losses (380)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(547)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity Securities, Fair Value Impaired Less Than 12 Months 6,111us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
2,138us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity Securities, Unrealized Loss Less Than 12 Months (42)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateAccumulatedLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(7)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateAccumulatedLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value 10,253us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
16,916us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses $ (338)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateAccumulatedLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
$ (540)dnbf_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateAccumulatedLoss
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember