| **Discontinued Operations (Tables)**                          | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|---------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
||
| **Discontinued Operation, Additional Disclosures [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Schedule of Assets and Liabilities of Discontinued Operations | Assets and liabilities of discontinued operations as of December 31, 2011 were as follows:(dollars in thousands)December 31, 2011Assets Loans held for sale$233Premises and equipment, net5Other real estate owned—Other assets7Assets of discontinued operations$245Liabilities Other liabilities$1,092Liabilities of discontinued operations$1,092                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| Schedule of Net Income (Loss) from Discontinued Operations    | Net (loss)/income from discontinued operations, net of tax, for the years ended December 31, 2012, 2011, and 2010 were as follows:(dollars in thousands) For the Twelve Months EndedDecember 31,  2012 2011 2010Interest Income      Interest and fees on loans $— $67 $552Total interest income — 67 552Interest Expense      Other borrowed funds — — —Total interest expense — — —Net Interest Income before Provision for Loan Losses — 67 552Provision for loan losses — — —Net Interest Income after Provision for Loan Losses — 67 552Noninterest Income      Mortgage loan (loss)/income — (167) 3,390Other service charges, commissions and fees, net — (11) (37)Other income — 10 12Total noninterest (loss)/income — (168) 3,365Noninterest Expense      Personnel expense 1 1,444 4,429Net occupancy expense 1 237 263Furniture, equipment and data processing expense — 186 312Professional fees 25 257 228Stationery, printing and supplies — 8 35Advertising and marketing — 27 155Other real estate owned expense — 166 —Provision for recourse loans — 3,317 666Other expense — 266 (765)Total noninterest expense 27 5,908 5,323Loss before income taxes (27) (6,009) (1,406)Income tax benefit — (213) —Net Loss from Discontinued Operations, net of tax $(27) $(5,796) $(1,406) |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of disposal groups, which may include the classification and carrying value of the assets and liabilities comprising the disposal group, and the segment in which the disposal group was reported.
+ References
No definition available.
+ Details**Name:**fnbn_ScheduleOfDisposalGroupsIncludingDiscontinuedOperationsBalanceSheetDisclosureTableTextBlock**Namespace Prefix:**fnbn_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of disposal groups, which may include the gain (loss) recognized in the income statement and the income statement caption that includes that gain (loss), amounts of revenues and pretax profit or loss reported in discontinued operations.
+ References
No definition available.
+ Details**Name:**fnbn_ScheduleOfDisposalGroupsIncludingDiscontinuedOperationsIncomeStatementDisclosureTableTextBlock**Namespace Prefix:**fnbn_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DiscontinuedOperationAdditionalDisclosuresAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |