| **Common Dividends**            | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
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| **Common Dividends [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| Common Dividends                | Common DividendsFNB is a legal entity separate and distinct from its banking and other subsidiaries and has in the past relied on dividends from CommunityOne as its primary source of liquidity. The CommunityOne Order, the Granite Order and the Written Agreement have prohibited CommunityOne and Granite from declaring or paying any dividends, or lending or otherwise supplying funds to FNB to meet FNB's obligations.FNB did not declare any dividends with respect to its common stock in 2012, 2011 or 2010. |

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| - Definition
Common Stock [Text Block]
+ References
No definition available.
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