Loans - Schedule of Recorded Investment in Criticized Loans by Class and Credit Quality Indicator (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	$ 5,416,750	$ 5,193,321
Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,834,445	1,793,258
Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	208,512	224,066
Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	147,896	111,763
Commercial Construction
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	125,589	94,890
Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	481,997	430,719
Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,027,393	1,032,851
Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	170,248	156,234
Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	3,514,083	3,413,062
Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	752,409	622,529
Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	148,087	153,717
Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	69,770	68,107
Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	797,942	792,416
Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	132,858	142,151
Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	970,266	844,353
Special Mention [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	163,581	127,270
Special Mention [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	85,292	61,787
Special Mention [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	13,414	16,593
Special Mention [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	412	1,640
Special Mention [Member] | Commercial Construction
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,555	166
Special Mention [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	15,381	18,399
Special Mention [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	5,038	4,453
Special Mention [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	3,831	6,114
Special Mention [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	109,542	90,753
Special Mention [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	778	644
Special Mention [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	681	651
Special Mention [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	46,402	32,975
Special Mention [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	6,178	2,247
Special Mention [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,459	1,295
Substandard [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	172,325	162,785
Substandard [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	85,293	84,556
Substandard [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	6,214	12,482
Substandard [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,621	1,886
Substandard [Member] | Commercial Construction
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	6,344	323
Substandard [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	14,179	14,691
Substandard [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	12,472	9,661
Substandard [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	17,813	16,529
Substandard [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	129,757	125,437
Substandard [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,527	1,131
Substandard [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,036	1,130
Substandard [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	29,281	27,982
Substandard [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	10,724	7,105
Substandard [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	2,563	2,261
Doubtful [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	36,336	30,350
Doubtful [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	10,842	10,609
Doubtful [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,401	591
Doubtful [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	656	0
Doubtful [Member] | Commercial Construction
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	664	756
Doubtful [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	2,721	1,347
Doubtful [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	764	2,540
Doubtful [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	0	0
Doubtful [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	14,327	14,496
Doubtful [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	101	154
Doubtful [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	264	198
Doubtful [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	21,240	15,085
Doubtful [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	404	417
Doubtful [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	365	352
Total Criticized Loans [Member]
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	372,242	320,405
Total Criticized Loans [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	181,427	156,952
Total Criticized Loans [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	21,029	29,666
Total Criticized Loans [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	2,689	3,526
Total Criticized Loans [Member] | Commercial Construction
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	8,563	1,245
Total Criticized Loans [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	32,281	34,437
Total Criticized Loans [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	18,274	16,654
Total Criticized Loans [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	21,644	22,643
Total Criticized Loans [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	253,626	230,686
Total Criticized Loans [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	2,406	1,929
Total Criticized Loans [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	1,981	1,979
Total Criticized Loans [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	96,923	76,042
Total Criticized Loans [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	17,306	9,769
Total Criticized Loans [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans
Loans held for investment	$ 4,387	$ 3,908