Shareholders' Equity (Share-based Compensation - Narrative) (Details) (USD $)	12 Months Ended							12 Months Ended					0 Months Ended	12 Months Ended		0 Months Ended		12 Months Ended			12 Months Ended
	Dec. 31, 2012 plan	Dec. 31, 2011 plan	Dec. 31, 2010 plan	Dec. 31, 2012 Granite Corp. [Member]	Dec. 31, 2011 Granite Corp. [Member]	Dec. 31, 2012 Integrity Financial Corporation [Member]	Dec. 31, 2006 Integrity Financial Corporation [Member] plan	Dec. 31, 2012 Restricted stock [Member]	Dec. 31, 2011 Restricted stock [Member]	Dec. 31, 2010 Restricted stock [Member]	Dec. 31, 2012 Restricted stock [Member] Later of Lifting of Consent Orders or Second Anniversary of Date of Grant [Member]	Dec. 31, 2012 Restricted stock [Member] Later of Lifting of Consent Orders or Third Anniversary of Date of Grant [Member]	Dec. 28, 2012 Restricted stock [Member] Officer [Member] officer	Dec. 31, 2012 Stock options [Member]	Dec. 31, 2012 2012 Incentive Plan [Member]	Dec. 28, 2012 2012 Incentive Plan [Member] Restricted stock [Member] Officer [Member] officer	Dec. 31, 2011 1993 stock compensation plan [Member]	Dec. 31, 2012 1993 stock compensation plan [Member] Stock options [Member]	Dec. 31, 2012 1993 stock compensation plan [Member] Stock options [Member] Maximum [Member]	Dec. 31, 2011 2003 stock compensation plan [Member]	Dec. 31, 2012 2003 stock compensation plan [Member] Stock options [Member]	Dec. 31, 2012 2003 stock compensation plan [Member] Stock options [Member] Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based compensation plans	5	5	5				3
Share-based compensation expense	$ 3,000	$ 23,000	$ 50,000
Share-based compensation expense related income tax benefit	1,000	9,000	7,000
Shares authorized for issuance															600,000
Maximum number of shares of FNB common stock each employee may be granted during any calendar year period															50,000
Awards granted (in shares)								110,059	0				110,059			110,059
Number of officers granted													6			6
Award become exercisable period																		1 year			1 year
Award vesting period																		5 years			5 years
Award expiration period																			10 years			10 years
Number of shares available for grants						0											0			8,243
Maximum number of shares of common stock reserved for issuance						235											729			10,985
Stock options assumed from acquisition (in shares)	0	78	0		78
Stock options exercisable (in shares)				0
Stock options expired (in shares)				78
Stock options granted (in shares)	0	0	0
Stock options exercised, intrinsic value	0	0	0
Stock options vested, grant date fair value	0	0	0
Stock options exercised (in shares)	0	0	0
Awards vested, fair value								1,040	1,040	114,600
Award vesting percentage											66.67%	33.33%
Unrecognized compensation cost related to non-vested share-based compensation arrangements	$ 1,200,000
Black-Scholes option pricing model, fair value assumptions:
Expected volatility, period of historical volatility														6 years
Expected life of options														6 years