Loans - Schedule of Loans by Class (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Loans and Leases Receivable
Loans held for investment	$ 5,193,321	$ 4,856,615
Mortgage loans held for sale	52,875	40,828
Total loans	5,246,196	4,897,443
Land acquisition & development construction real estate
Loans and Leases Receivable
Loans held for investment	224,066	220,443
Residential construction real estate
Loans and Leases Receivable
Loans held for investment	111,763	96,580
Commercial Construction
Loans and Leases Receivable
Loans held for investment	94,890	101,246
Total construction loans
Loans and Leases Receivable
Loans held for investment	430,719	418,269
Residential real estate
Loans and Leases Receivable
Loans held for investment	$ 1,032,851	999,903
Loans receivable, maturity	15 years
Agricultural real estate
Loans and Leases Receivable
Loans held for investment	$ 156,234	167,659
Total real estate loans
Loans and Leases Receivable
Loans held for investment	3,413,062	3,225,253
Indirect consumer
Loans and Leases Receivable
Loans held for investment	622,529	552,863
Other consumer
Loans and Leases Receivable
Loans held for investment	153,717	144,141
Credit card consumer
Loans and Leases Receivable
Loans held for investment	68,107	65,467
Total consumer loans
Loans and Leases Receivable
Loans held for investment	844,353	762,471
Commercial
Loans and Leases Receivable
Loans held for investment	792,416	740,073
Agricultural
Loans and Leases Receivable
Loans held for investment	142,151	124,859
Other, including overdrafts
Loans and Leases Receivable
Loans held for investment	1,339	3,959
Commercial real estate
Loans and Leases Receivable
Loans held for investment	$ 1,793,258	1,639,422
Loans receivable, maturity	5 years
Loans held for investment
Loans and Leases Receivable
Loans held for investment	$ 5,193,321	4,856,615
Total loans
Loans and Leases Receivable
Total loans	5,246,196	4,897,443
Home equity line of credit
Loans and Leases Receivable
Loans held for investment	$ 298,661	$ 298,692
Loans receivable, loan to value limit	80.00%