Schedule of Loans by Class (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 5,120,794	$ 4,856,615
Mortgage loans held for sale	55,686	40,828
Total loans	5,176,480	4,897,443
Commercial real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,750,797	1,639,422
Land acquisition & development construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	212,990	220,443
Residential construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	112,495	96,580
Commercial construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	93,775	101,246
Total construction loans
Loans and Leases Receivable [Line Items]
Loans held for investment	419,260	418,269
Residential real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,020,445	999,903
Agricultural real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	163,116	167,659
Total real estate loans
Loans and Leases Receivable [Line Items]
Loans held for investment	3,353,618	3,225,253
Indirect consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	616,142	552,863
Other consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	150,170	144,141
Credit card consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	65,649	65,467
Total consumer loans
Loans and Leases Receivable [Line Items]
Loans held for investment	831,961	762,471
Total loans	831,961	762,471
Commercial
Loans and Leases Receivable [Line Items]
Loans held for investment	778,648	740,073
Total loans	778,648	740,073
Agricultural
Loans and Leases Receivable [Line Items]
Loans held for investment	154,855	124,859
Other, including overdrafts
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 1,712	$ 3,959