Loans and Allowance - Summary of Troubled Debt Restructurings by Modification Type (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Financing Receivable, Modifications [Line Items]
Modification	$ 638	$ 4,788	$ 993	$ 5,494
Term Modification
Financing Receivable, Modifications [Line Items]
Modification	41	1,559	41	1,559
Rate Modification
Financing Receivable, Modifications [Line Items]
Modification	385	143	505	304
Combination
Financing Receivable, Modifications [Line Items]
Modification	212	3,086	447	3,631
Commercial and industrial loans
Financing Receivable, Modifications [Line Items]
Modification	169		169	198
Commercial and industrial loans | Term Modification
Financing Receivable, Modifications [Line Items]
Modification
Commercial and industrial loans | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification
Commercial and industrial loans | Combination
Financing Receivable, Modifications [Line Items]
Modification	169		169	198
Agricultural production financing and other loans to farmers
Financing Receivable, Modifications [Line Items]
Modification		1,141		1,190
Agricultural production financing and other loans to farmers | Term Modification
Financing Receivable, Modifications [Line Items]
Modification		1,141		1,141
Agricultural production financing and other loans to farmers | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification				49
Commercial and farmland
Financing Receivable, Modifications [Line Items]
Modification	195	3,504	430	3,851
Commercial and farmland | Term Modification
Financing Receivable, Modifications [Line Items]
Modification	41	418	41	418
Commercial and farmland | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification	154		154
Commercial and farmland | Combination
Financing Receivable, Modifications [Line Items]
Modification		3,086	235	3,433
Real estate loans - Residential
Financing Receivable, Modifications [Line Items]
Modification	274		394	112
Real estate loans - Residential | Term Modification
Financing Receivable, Modifications [Line Items]
Modification
Real estate loans - Residential | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification	231		351	112
Real estate loans - Residential | Combination
Financing Receivable, Modifications [Line Items]
Modification	$ 43		$ 43
Real estate loans - Home equity
Financing Receivable, Modifications [Line Items]
Modification		143		143
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		143		143
Real estate loans - Home equity | Combination
Financing Receivable, Modifications [Line Items]
Modification