Covered Assets and Indemnification Asset (Details) (USD $)	0 Months Ended
	Sep. 13, 2013	Sep. 13, 2013	Mar. 31, 2015	Dec. 31, 2014
Loans
Allowance for covered loans			$ (1,388,000)	$ (4,611,000)
Total covered loans, net of allowance			550,626,000	638,029,000
Covered
Loans
Total covered loans			552,014,000	642,640,000
Allowance for covered loans			(1,388,000)	(4,611,000)
Total covered loans, net of allowance			550,626,000	638,029,000
Covered | Commercial and industrial
Loans
Total covered loans			22,349,000	30,780,000
Covered | Real estate
Loans
Total covered loans			478,040,000	552,850,000
Covered | Construction and land development
Loans
Total covered loans			51,625,000	59,010,000
Bank | Covered | Acquired loans
Loans
Fair value of loans acquired	1,100,000,000	1,100,000,000
Carryover of the allowance for loan losses recorded	0
Bank | FNB
Loans
Percentage of losses to be absorbed by FDIC on the first $240.4 million of losses incurred as per the loss sharing agreement	80.00%	80.00%
Threshold amount of losses incurred for 80% of losses to be absorbed by FDIC as per the loss sharing agreement, first layer	240,400,000	240,400,000
Percentage of losses to be absorbed by FDIC in excess of $240.4 million up to and including $365.7 million of losses incurred as per the loss sharing agreement	0.00%	0.00%
Threshold amount of losses incurred for 0% of losses to be absorbed by FDIC as per the loss sharing agreement, second layer	$ 365,700,000	$ 365,700,000
Percentage of losses to be absorbed by FDIC in excess of $365.7 million of losses incurred as per the loss sharing agreement	80.00%	80.00%
Period for which payment is required to be made to the FDIC of true-up amount	10 years
Bank | FNB | Covered | Commercial loan
Loans
Period of loss-sharing agreements in effect	5 years
Period of loss recovery provisions in effect	8 years
Bank | FNB | Covered | Single family residential loans
Loans
Period of loss-sharing agreements in effect	10 years
Period of loss recovery provisions in effect	10 years