Investment Securities, Securities Held-to-Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Book value	$ 69,036	$ 60,229	$ 60,310
Gross unrealized gains	1,158	880	845
Gross unrealized losses	0	12	0
Fair value	70,194	61,097	61,155
Obligations of States and Political Subdivisions [Member]
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Book value	69,036	60,229	60,310
Gross unrealized gains	1,158	880	845
Gross unrealized losses	0	12	0
Fair value	$ 70,194	$ 61,097	$ 61,155