Loans and Allowance for Loan Losses (Unfunded Commitment) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Unfunded Commitments [Abstract]
Utilization rate on letters of credit	10.00%
Reserve for unfunded commitments	$ 0.6	$ 0.6

The amount of reserve for unfunded commitments for which the entity is obligated, to lend.

No definition available.

Name:	fnbn_LoansAndLeasesReceivableUnfundedCommitmentsReserve
Namespace Prefix:	fnbn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant