Investment Securities, Securities Held-to-Maturity (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Amortized cost		$ 737,052	$ 68,933
Gross unrealized gains		782	1,116
Gross unrealized losses		11,993	0
Fair value		725,841	70,049
Municipal Securities [Member]
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Amortized cost		66,496	68,933
Gross unrealized gains		701	1,116
Gross unrealized losses		0	0
Fair value		67,197	$ 70,049
Mortgage-backed Securities [Member]
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Amortized cost	[1]	596,775
Gross unrealized gains	[1]	45
Gross unrealized losses	[1]	11,764
Fair value	[1]	585,056
Collateralized Mortgage Obligations [Member]
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Amortized cost		73,781
Gross unrealized gains		36
Gross unrealized losses		229
Fair value		$ 73,588

[1] All mortgage-backed securities were issued by an agency or government sponsored entity of the U.S. Government.