Schedule of Recorded Investment in Criticized Loans by Class and Credit Quality Indicator (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	$ 5,462,936	$ 5,193,321
Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,843,120	1,793,258
Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	212,680	224,066
Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	137,014	111,763
Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	128,154	94,890
Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	477,848	430,719
Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,047,150	1,032,851
Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	172,949	156,234
Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	3,541,067	3,413,062
Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	731,901	622,529
Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	153,624	153,717
Credit card consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	66,860	68,107
Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	952,385	844,353
Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	814,392	792,416
Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	152,800	142,151
Other Assets Especially Mentioned
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	152,868	127,270
Other Assets Especially Mentioned | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	76,913	61,787
Other Assets Especially Mentioned | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	11,597	16,593
Other Assets Especially Mentioned | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,615	1,640
Other Assets Especially Mentioned | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,616	166
Other Assets Especially Mentioned | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	14,828	18,399
Other Assets Especially Mentioned | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	5,461	4,453
Other Assets Especially Mentioned | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	6,511	6,114
Other Assets Especially Mentioned | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	103,713	90,753
Other Assets Especially Mentioned | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	847	644
Other Assets Especially Mentioned | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	665	651
Other Assets Especially Mentioned | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,512	1,295
Other Assets Especially Mentioned | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	42,080	32,975
Other Assets Especially Mentioned | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	5,563	2,247
Substandard
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	175,555	162,785
Substandard | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	88,580	84,556
Substandard | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	7,377	12,482
Substandard | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,482	1,886
Substandard | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	5,891	323
Substandard | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	14,750	14,691
Substandard | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	13,195	9,661
Substandard | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	16,605	16,529
Substandard | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	133,130	125,437
Substandard | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,572	1,131
Substandard | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,130	1,130
Substandard | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,702	2,261
Substandard | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	31,931	27,982
Substandard | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	7,792	7,105
Doubtful
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	41,540	30,350
Doubtful | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	17,991	10,609
Doubtful | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	1,383	591
Doubtful | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	664	0
Doubtful | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	720	756
Doubtful | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,767	1,347
Doubtful | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	214	2,540
Doubtful | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	0	0
Doubtful | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	20,972	14,496
Doubtful | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	121	154
Doubtful | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	217	198
Doubtful | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	338	352
Doubtful | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	19,758	15,085
Doubtful | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	472	417
Total Criticized Loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	369,963	320,405
Total Criticized Loans | Commercial real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	183,484	156,952
Total Criticized Loans | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	20,357	29,666
Total Criticized Loans | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	3,761	3,526
Total Criticized Loans | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	8,227	1,245
Total Criticized Loans | Total construction loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	32,345	34,437
Total Criticized Loans | Residential real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	18,870	16,654
Total Criticized Loans | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	23,116	22,643
Total Criticized Loans | Total real estate loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	257,815	230,686
Total Criticized Loans | Indirect consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,540	1,929
Total Criticized Loans | Other consumer
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	2,012	1,979
Total Criticized Loans | Total consumer loans
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	4,552	3,908
Total Criticized Loans | Commercial
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	93,769	76,042
Total Criticized Loans | Agricultural
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]
Loans held for investment	$ 13,827	$ 9,769