Loans and the Allowance for Loan Losses (Details 8) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014		Sep. 01, 2013
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	$ 321,426		$ 344,425		$ 899,236
Impaired Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	7,796		8,004
Other Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	117,977		135,037
Not Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	195,653		201,384
Commercial, financial, agricultural
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	20,657		23,404
Commercial, financial, agricultural | Impaired Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	0		0
Commercial, financial, agricultural | Other Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	3,917		6,684
Commercial, financial, agricultural | Not Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	16,740		16,720
Lease financing
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	0		0
Lease financing | Impaired Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	0		0
Lease financing | Other Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	0		0
Lease financing | Not Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	0		0
Real estate – construction
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	0		0
Real estate – construction | Impaired Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	0		0
Real estate – construction | Other Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	0		0
Real estate – construction | Not Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	0		0
Real estate – 1-4 family mortgage
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	80,292		82,819
Real estate – 1-4 family mortgage | Impaired Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	420		420
Real estate – 1-4 family mortgage | Other Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	42,338		43,597
Real estate – 1-4 family mortgage | Not Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	37,534		38,802
Real estate – commercial mortgage
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	216,851		234,245
Real estate – commercial mortgage | Impaired Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	7,376		7,584
Real estate – commercial mortgage | Other Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	71,688		84,720
Real estate – commercial mortgage | Not Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	137,787		141,941
Installment loans to individuals
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	3,626	[1]	3,957	[1]
Installment loans to individuals | Impaired Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	0		0
Installment loans to individuals | Other Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	34		36
Installment loans to individuals | Not Covered Loans
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality	3,592		3,921
Contractually-required principal and interest
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality					1,112,979
Nonaccretable difference
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality					70,334
Cash flows expected to be collected
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality					1,042,645
Accretable yield
Loans acquired with deteriorated credit quality
Acquired with deteriorated credit quality					$ 143,409

[1] Includes lease financing receivables.