Loans and Allowance - Summary of Non-Accrual Loans by Loan Class (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 32,253	$ 29,998
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	4,910	1,839
Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	1,282	1,329
Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	67	73
Real estate loans - Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	12,152	15,754
Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	11,973	9,523
Real estate loans - Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	1,818	1,457
Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 51	$ 23