Investment Securities - Total Gross Proceeds from Sales of Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Available for sale (AFS):
Available-for-sale securities, gross realized gains	$ 21	$ 19
Available-for-sale securities, gross realized losses	0	6
State and political securities
Available for sale (AFS):
Available-for-sale securities, gross realized gains	1	15
Available-for-sale securities, gross realized losses	0	2
Other debt securities
Available for sale (AFS):
Available-for-sale securities, gross realized gains	20	4
Available-for-sale securities, gross realized losses	$ 0	$ 4