Schedule of Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 4,093,815	$ 4,133,028
Mortgage loans held for sale	76,148	53,521
Total loans	4,169,963	4,186,549	4,281,260
Commercial real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,517,400	1,553,155
Land acquisition & development construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	240,550	278,613
Residential construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	51,193	61,106
Commercial construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	59,911	61,054
Total construction loans
Loans and Leases Receivable [Line Items]
Loans held for investment	351,654	400,773
Residential real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	572,018	571,943
Agricultural real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	171,087	175,302
Total real estate loans
Loans and Leases Receivable [Line Items]
Loans held for investment	2,612,159	2,701,173
Indirect consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	418,604	407,651
Other consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	144,442	147,487
Credit card consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	58,166	60,933
Total consumer loans
Loans and Leases Receivable [Line Items]
Loans held for investment	621,212	616,071
Commercial
Loans and Leases Receivable [Line Items]
Loans held for investment	720,010	693,261
Agricultural
Loans and Leases Receivable [Line Items]
Loans held for investment	138,115	119,710
Other, including overdrafts
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 2,319	$ 2,813