Fair Value - Assets and Liabilities Measured at Fair Value on Non-Recurring Basis (Details) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Commercial, industrial, and agricultural
Impaired loans:
Assets, fair value disclosure	$ 687	$ 2,055
Commercial, industrial, and agricultural | Quoted Prices in Active Markets for Identical Assets
Impaired loans:
Assets, fair value disclosure	0	0
Commercial, industrial, and agricultural | Significant Other Observable Inputs
Impaired loans:
Assets, fair value disclosure	0	0
Commercial, industrial, and agricultural | Significant Unobservable Inputs
Impaired loans:
Assets, fair value disclosure	687	2,055
Commercial mortgages
Impaired loans:
Assets, fair value disclosure	1,089	679
Commercial mortgages | Quoted Prices in Active Markets for Identical Assets
Impaired loans:
Assets, fair value disclosure	0	0
Commercial mortgages | Significant Other Observable Inputs
Impaired loans:
Assets, fair value disclosure	0	0
Commercial mortgages | Significant Unobservable Inputs
Impaired loans:
Assets, fair value disclosure	$ 1,089	$ 679