Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Consolidated Statements of Comprehensive Income [Abstract]
Accretion Of Discount On Available For Sale To Held To Maturity Reclassification, Tax Expense	$ 1	$ 3

Accretion Of Discount On Available For Sale To Held To Maturity Reclassification, Tax Expense

No definition available.

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