Investment Securities - Total Gross Proceeds from Sales of Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Available for sale (AFS)
Available-for-sale securities, gross realized gains	$ 19	$ 0
Available-for-sale securities, gross realized losses	6	9
State and political securities
Available for sale (AFS)
Available-for-sale securities, gross realized gains	15	0
Available-for-sale securities, gross realized losses	2	9
Other debt securities
Available for sale (AFS)
Available-for-sale securities, gross realized gains	4	0
Available-for-sale securities, gross realized losses	$ 4	$ 0