Schedule of Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 4,279,959	$ 4,157,470
Mortgage loans held for sale	52,133	66,442
Total loans	4,332,092	4,223,912	4,180,051
Commercial real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,441,297	1,497,272
Land acquisition & development construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	210,153	220,196
Residential construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	68,362	49,274
Commercial construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	62,769	65,059
Total construction loans
Loans and Leases Receivable [Line Items]
Loans held for investment	341,284	334,529
Residential real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	841,707	708,339
Agricultural real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	176,594	177,244
Total real estate loans
Loans and Leases Receivable [Line Items]
Loans held for investment	2,800,882	2,717,384
Indirect consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	476,531	438,245
Other consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	135,638	137,743
Credit card consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	60,015	60,806
Total consumer loans
Loans and Leases Receivable [Line Items]
Loans held for investment	672,184	636,794
Commercial
Loans and Leases Receivable [Line Items]
Loans held for investment	681,416	688,753
Agricultural
Loans and Leases Receivable [Line Items]
Loans held for investment	123,565	113,627
Other, including overdrafts
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 1,912	$ 912