Schedule of Loans by Class (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 5,376,542	$ 5,416,750
Mortgage loans held for sale	23,237	61,794
Total loans	5,399,779	5,478,544
Commercial real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,819,654	1,834,445
Land acquisition & development construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	200,412	208,512
Residential construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	143,852	147,896
Commercial construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	121,154	125,589
Total construction loans
Loans and Leases Receivable [Line Items]
Loans held for investment	465,418	481,997
Residential real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,004,045	1,027,393
Agricultural real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	167,749	170,248
Total real estate loans
Loans and Leases Receivable [Line Items]
Loans held for investment	3,456,866	3,514,083
Indirect consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	762,477	752,409
Other consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	145,443	148,087
Credit card consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	65,241	69,770
Total consumer loans
Loans and Leases Receivable [Line Items]
Loans held for investment	973,161	970,266
Commercial
Loans and Leases Receivable [Line Items]
Loans held for investment	817,841	797,942
Agricultural
Loans and Leases Receivable [Line Items]
Loans held for investment	125,492	132,858
Other, including overdrafts
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 3,182	$ 1,601