| **Deposits (Details Textual) (USD $)**                       | 12 Months Ended |
|--------------------------------------------------------------|-----------------|
||
| **Deposits [Abstract]**                                      |            |   |   |
| Brokered deposits included in jumbo certificates of deposit  | $ 0             | $ 200,000 |   |
| Minimum denomination                                         | 100,000         |   |   |
| Time seposits at minimum denominations of $100,000           | 290,166,000     | 394,238,000 |   |
| jumbo time deposits including brokered                       |            | 394,400,000 |   |
| Overdrawn transaction deposit accounts reclassified to loans | 400,000         | 400,000 |   |
| Interest expense on time deposits of $100,000 or more        | $ 5,000,000     | $ 6,100,000 | $ 8,300,000 |
| Basis points over the prevailing interest rates              | 0.75%           |   |   |

| X                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Brokered Deposits Included in Jumbo Certificates of Deposit
+ References
No definition available.
+ Details**Name:**fnbn_BrokeredDepositsIncludedInJumboCertificatesOfDeposit**Namespace Prefix:**fnbn_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
jumbo time deposits including brokered
+ References
No definition available.
+ Details**Name:**fnbn_JumboTimeDepositsIncludingBrokered**Namespace Prefix:**fnbn_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Minimum Denomination
+ References
No definition available.
+ Details**Name:**fnbn_MinimumDenomination**Namespace Prefix:**fnbn_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Overdrawn Transaction Deposits
+ References
No definition available.
+ Details**Name:**fnbn_OverdrawnTransactionDeposits**Namespace Prefix:**fnbn_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Rates on Deposits, Basis Points over Prevailing Interest Rates
+ References
No definition available.
+ Details**Name:**fnbn_RatesOnDepositsBasisPointsOverPrevailingInterestRates**Namespace Prefix:**fnbn_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**instant |
| X                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DepositsAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Interest expense incurred on time deposits, including certificates of deposits, of $100,000 or more in domestic offices.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.6) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 6 -Article 9Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher OTS -Name Federal Regulation (FR) -Number Title 12 -Section 563c.102 -Paragraph 6 -Chapter V -Subsection II -LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy.  It will be removed from future versions of this taxonomy.
+ Details**Name:**us-gaap_InterestExpenseTimeDeposits100000OrMore**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The aggregate amount of domestic time deposits (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 405 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6479006&loc=d3e64164-112818Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 01-6 -Paragraph 14 -Subparagraph e -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.
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