Loans and Allowance - Summary of Troubled Debt Restructurings by Modification Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Modifications [Line Items]
Modification	$ 205	$ 200	$ 606	$ 1,088
Term Modification
Financing Receivable, Modifications [Line Items]
Modification		5	77	46
Rate Modification
Financing Receivable, Modifications [Line Items]
Modification	112	195	290	600
Combination
Financing Receivable, Modifications [Line Items]
Modification	93		239	442
Commercial and industrial loans
Financing Receivable, Modifications [Line Items]
Modification		5		173
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
Commercial and farmland
Financing Receivable, Modifications [Line Items]
Modification				334
Commercial and farmland | Term Modification
Financing Receivable, Modifications [Line Items]
Modification				41
Commercial and farmland | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification				61
Commercial and farmland | Combination
Financing Receivable, Modifications [Line Items]
Modification				232
Residential
Financing Receivable, Modifications [Line Items]
Modification	140	122	447	508
Residential | Term Modification
Financing Receivable, Modifications [Line Items]
Modification
Residential | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification	47	122	208	466
Residential | Combination
Financing Receivable, Modifications [Line Items]
Modification	93		239	42
Home equity
Financing Receivable, Modifications [Line Items]
Modification	65	73	153	73
Home equity | Term Modification
Financing Receivable, Modifications [Line Items]
Modification			77
Home equity | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification	65	73	76	73
Home equity | Combination
Financing Receivable, Modifications [Line Items]
Modification
Individuals' loans for household and other personal expenditures
Financing Receivable, Modifications [Line Items]
Modification			6
Individuals' loans for household and other personal expenditures | Rate Modification
Financing Receivable, Modifications [Line Items]
Modification			6
Individuals' loans for household and other personal expenditures | Combination
Financing Receivable, Modifications [Line Items]
Modification