Consolidated Statements of Cash Flows (Parenthetical) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Consolidated Statements of Cash Flows
Available-For-Sale Securities, Transfers to Held-To-Maturity, Amortized Cost	$ 20

Available-For-Sale Securities, Transfers to Held-To-Maturity, Amortized Cost

No definition available.

Name:	dnbf_AvailableForSaleSecuritiesTransfersToHeldToMaturityAmortizedCost
Namespace Prefix:	dnbf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant