Schedule of Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 4,326,367	$ 4,303,992
Mortgage loans held for sale	38,471	40,861
Total loans	4,364,838	4,344,853	4,224,559
Commercial real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,452,967	1,449,174
Land acquisition & development construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	197,582	205,911
Residential construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	81,411	76,488
Commercial construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	75,356	69,236
Total construction loans
Loans and Leases Receivable [Line Items]
Loans held for investment	354,349	351,635
Residential real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	868,836	867,912
Agricultural real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	160,570	173,534
Total real estate loans
Loans and Leases Receivable [Line Items]
Loans held for investment	2,836,722	2,842,255
Indirect consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	481,482	476,012
Other consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	130,614	133,039
Credit card consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	58,310	62,536
Total consumer loans
Loans and Leases Receivable [Line Items]
Loans held for investment	670,406	671,587
Commercial
Loans and Leases Receivable [Line Items]
Loans held for investment	707,237	676,544
Agricultural
Loans and Leases Receivable [Line Items]
Loans held for investment	108,376	111,872
Other, including overdrafts
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 3,626	$ 1,734