Schedule of Loans by Class (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 5,028,624	$ 4,856,615
Mortgage loans held for sale	75,322	40,828
Total loans	5,103,946	4,897,443
Commercial real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,704,073	1,639,422
Land acquisition & development construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	211,889	220,443
Residential construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	101,023	96,580
Commercial construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	90,316	101,246
Total construction loans
Loans and Leases Receivable [Line Items]
Loans held for investment	403,228	418,269
Residential real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	999,038	999,903
Agricultural real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	158,506	167,659
Total real estate loans
Loans and Leases Receivable [Line Items]
Loans held for investment	3,264,845	3,225,253
Indirect consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	589,479	552,863
Other consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	144,919	144,141
Credit card consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	64,728	65,467
Total consumer loans
Loans and Leases Receivable [Line Items]
Loans held for investment	799,126	762,471
Total loans	799,126	762,471
Commercial
Loans and Leases Receivable [Line Items]
Loans held for investment	819,119	740,073
Total loans	819,119	740,073
Agricultural
Loans and Leases Receivable [Line Items]
Loans held for investment	142,629	124,859
Other, including overdrafts
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 2,905	$ 3,959