Schedule of Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 4,107,171	$ 4,133,028
Mortgage loans held for sale	72,880	53,521
Total loans	4,180,051	4,186,549	4,275,717
Commercial real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,513,784	1,553,155
Land acquisition & development construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	233,082	278,613
Residential construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	50,895	61,106
Commercial construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	56,097	61,054
Total construction loans
Loans and Leases Receivable [Line Items]
Loans held for investment	340,074	400,773
Residential real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	639,235	571,943
Agricultural real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	175,395	175,302
Total real estate loans
Loans and Leases Receivable [Line Items]
Loans held for investment	2,668,488	2,701,173
Indirect consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	431,449	407,651
Other consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	139,984	147,487
Credit card consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	58,324	60,933
Total consumer loans
Loans and Leases Receivable [Line Items]
Loans held for investment	629,757	616,071
Commercial
Loans and Leases Receivable [Line Items]
Loans held for investment	672,100	693,261
Agricultural
Loans and Leases Receivable [Line Items]
Loans held for investment	135,467	119,710
Other, including overdrafts
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 1,359	$ 2,813