Investment Securities, Securities Held-to-Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Amortized cost	$ 68,933	$ 60,229
Gross unrealized gains	1,116	880
Gross unrealized losses	0	12
Fair value	70,049	61,097
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]
Amortized cost	68,933	60,229
Gross unrealized gains	1,116	880
Gross unrealized losses	0	12
Fair value	$ 70,049	$ 61,097