Loans and Allowance - Credit Quality of Loan Portfolio by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 5,139,645	$ 4,693,822
Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	1,194,646	1,057,075
Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	79,689	97,711
Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	418,703	366,704
Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	1,953,062	1,802,921
Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	739,169	786,105
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	418,525	348,613
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans	77,479	74,717
Finance Leases
Financing Receivable, Recorded Investment [Line Items]
Loans	311	588
Other commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	258,061	159,388
Commercial Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	3,769,920	3,404,491
Commercial Pass | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	1,117,545	962,340
Commercial Pass | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	30,712	77,884
Commercial Pass | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	398,646	345,449
Commercial Pass | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	1,811,367	1,679,141
Commercial Pass | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	146,251	171,576
Commercial Pass | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	7,310	8,218
Commercial Pass | Finance Leases
Financing Receivable, Recorded Investment [Line Items]
Loans	228	495
Commercial Pass | Other commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	257,861	159,388
Commercial Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	124,863	105,965
Commercial Special Mention | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	30,919	48,432
Commercial Special Mention | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	25,273	6,665
Commercial Special Mention | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	3,490	1,271
Commercial Special Mention | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	60,028	46,442
Commercial Special Mention | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	5,106	3,107
Commercial Special Mention | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	47	48
Commercial Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans	159,215	149,395
Commercial Substandard | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	46,182	45,984
Commercial Substandard | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	23,704	13,162
Commercial Substandard | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	1,858	1,790
Commercial Substandard | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	80,626	77,338
Commercial Substandard | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	6,046	10,428
Commercial Substandard | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	516	600
Commercial Substandard | Finance Leases
Financing Receivable, Recorded Investment [Line Items]
Loans	83	93
Commercial Substandard | Other commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	200
Commercial Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans		319
Commercial Doubtful | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans		319
Commercial Doubtful | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans
Consumer Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	1,076,417	1,023,856
Consumer Performing | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	14,636	18,114
Consumer Performing | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	1,034
Consumer Performing | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	574,054	593,533
Consumer Performing | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	409,237	337,718
Consumer Performing | Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans	77,456	74,491
Consumer Non Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	9,230	9,796
Consumer Non Performing | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	73	80
Consumer Non Performing | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	7
Consumer Non Performing | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	7,712	7,461
Consumer Non Performing | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	1,415	2,029
Consumer Non Performing | Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 23	$ 226