Loans - Schedule of Recorded Investment in Criticized Loans by Class and Credit Quality Indicator (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	$ 5,193,321	$ 4,856,615
Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,793,258	1,639,422
Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	224,066	220,443
Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	111,763	96,580
Commercial Construction
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	94,890	101,246
Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	430,719	418,269
Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,032,851	999,903
Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	156,234	167,659
Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	3,413,062	3,225,253
Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	622,529	552,863
Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	153,717	144,141
Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	68,107	65,467
Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	792,416	740,073
Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	142,151	124,859
Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	844,353	762,471
Special Mention [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	127,270	154,084
Special Mention [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	61,787	84,533
Special Mention [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	16,593	11,826
Special Mention [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,640	2,029
Special Mention [Member] | Commercial Construction
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	166	39
Special Mention [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	18,399	13,894
Special Mention [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	4,453	10,473
Special Mention [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	6,114	10,122
Special Mention [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	90,753	119,022
Special Mention [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	644	916
Special Mention [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	651	553
Special Mention [Member] | Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment		0
Special Mention [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	32,975	25,766
Special Mention [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	2,247	7,827
Special Mention [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,295	1,469
Substandard [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	162,785	163,675
Substandard [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	84,556	83,448
Substandard [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	12,482	15,016
Substandard [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,886	2,666
Substandard [Member] | Commercial Construction
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	323	253
Substandard [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	14,691	17,935
Substandard [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	9,661	10,848
Substandard [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	16,529	12,328
Substandard [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	125,437	124,559
Substandard [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,131	1,590
Substandard [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,130	1,085
Substandard [Member] | Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment		348
Substandard [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	27,982	32,433
Substandard [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	7,105	3,660
Substandard [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	2,261	3,023
Doubtful [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	30,350	34,854
Doubtful [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	10,609	15,246
Doubtful [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	591	2,507
Doubtful [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	0	0
Doubtful [Member] | Commercial Construction
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	756	2,442
Doubtful [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,347	4,949
Doubtful [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	2,540	1,121
Doubtful [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	0	612
Doubtful [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	14,496	21,928
Doubtful [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	154	121
Doubtful [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	198	432
Doubtful [Member] | Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment		1,263
Doubtful [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	15,085	10,273
Doubtful [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	417	837
Doubtful [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	352	1,816
Total Criticized Loans [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	320,405	352,613
Total Criticized Loans [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	156,952	183,227
Total Criticized Loans [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	29,666	29,349
Total Criticized Loans [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	3,526	4,695
Total Criticized Loans [Member] | Commercial Construction
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,245	2,734
Total Criticized Loans [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	34,437	36,778
Total Criticized Loans [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	16,654	22,442
Total Criticized Loans [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	22,643	23,062
Total Criticized Loans [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	230,686	265,509
Total Criticized Loans [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,929	2,627
Total Criticized Loans [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,979	2,070
Total Criticized Loans [Member] | Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment		1,611
Total Criticized Loans [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	76,042	68,472
Total Criticized Loans [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	9,769	12,324
Total Criticized Loans [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	$ 3,908	$ 6,308