Schedule of Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 4,791,444	$ 4,303,992
Mortgage loans held for sale	62,938	40,861
Total loans	4,854,382	4,344,853	4,332,092
Commercial real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,686,509	1,449,174
Land acquisition & development construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	194,138	205,911
Residential construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	88,179	76,488
Commercial construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	85,103	69,236
Total construction loans
Loans and Leases Receivable [Line Items]
Loans held for investment	367,420	351,635
Residential real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	957,282	867,912
Agricultural real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	158,940	173,534
Total real estate loans
Loans and Leases Receivable [Line Items]
Loans held for investment	3,170,151	2,842,255
Indirect consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	537,765	476,012
Other consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	145,076	133,039
Credit card consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	62,641	62,536
Total consumer loans
Loans and Leases Receivable [Line Items]
Loans held for investment	745,482	671,587
Commercial
Loans and Leases Receivable [Line Items]
Loans held for investment	736,908	676,544
Agricultural
Loans and Leases Receivable [Line Items]
Loans held for investment	136,587	111,872
Other, including overdrafts
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 2,316	$ 1,734