Loans and Allowance - Summary of Troubled Debt Restructurings by Modification Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Modifications [Line Items]
Modification	$ 200	$ 814	$ 1,088	$ 5,968
Term Modification
Financing Receivable, Modifications [Line Items]
Modification	5		46	1,314
Rate Modification
Financing Receivable, Modifications [Line Items]
Modification	195	719	600	970
Combination
Financing Receivable, Modifications [Line Items]
Modification		95	442	3,684
Commercial and industrial loans
Financing Receivable, Modifications [Line Items]
Modification	5		173	197
Commercial and industrial loans | Term Modification
Financing Receivable, Modifications [Line Items]
Modification	5		5
Commercial and industrial loans | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification
Commercial and industrial loans | Combination
Financing Receivable, Modifications [Line Items]
Modification			168	197
Agricultural production financing and other loans to farmers
Financing Receivable, Modifications [Line Items]
Modification				898
Agricultural production financing and other loans to farmers | Term Modification
Financing Receivable, Modifications [Line Items]
Modification				898
Agricultural production financing and other loans to farmers | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification
Real estate loans - Commercial and farmland
Financing Receivable, Modifications [Line Items]
Modification		95	334	3,903
Real estate loans - Commercial and farmland | Term Modification
Financing Receivable, Modifications [Line Items]
Modification			41	416
Real estate loans - Commercial and farmland | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification			61
Real estate loans - Commercial and farmland | Combination
Financing Receivable, Modifications [Line Items]
Modification		95	232	3,487
Real estate loans - Residential
Financing Receivable, Modifications [Line Items]
Modification	122	663	508	773
Real estate loans - Residential | Term Modification
Financing Receivable, Modifications [Line Items]
Modification
Real estate loans - Residential | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification	122	663	466	773
Real estate loans - Residential | Combination
Financing Receivable, Modifications [Line Items]
Modification			42
Real estate loans - Home equity
Financing Receivable, Modifications [Line Items]
Modification	73	56	73	197
Real estate loans - Home equity | Term Modification
Financing Receivable, Modifications [Line Items]
Modification
Real estate loans - Home equity | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification	73	56	73	197
Real estate loans - Home equity | Combination
Financing Receivable, Modifications [Line Items]
Modification