Investment Securities, Securities Held-to-Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Book value	$ 69,913	$ 60,229	$ 60,354
Gross unrealized gains	1,142	880	946
Gross unrealized losses	0	12	7
Fair value	71,055	61,097	61,293
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	69,913	60,229	60,354
Gross unrealized gains	1,142	880	946
Gross unrealized losses	0	12	7
Fair value	$ 71,055	$ 61,097	$ 61,293