Investment Securities, Securities Held-to-Maturity (Details) - USD ($) $ in Thousands		Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Amortized cost		$ 817,688		$ 845,346
Gross unrealized gains		137		78
Gross unrealized losses		146,240		157,031
Fair value		671,585		688,393
Allowance for credit losses		450		393		$ 0
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]	664,728		702,858
Gross unrealized gains	[1]	30		29
Gross unrealized losses	[1]	132,043		141,121
Fair value	[1]	532,715		561,766
Allowance for credit losses		0	[1]	0	[1]	0
Collateralized Mortgage Obligations [Member]
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Amortized cost	[1]	74,170		80,186
Gross unrealized gains	[1]	0		0
Gross unrealized losses	[1]	14,017		15,701
Fair value	[1]	60,153		64,485
Allowance for credit losses		0	[1]	0	[1]	0
Municipal Securities [Member]
Book values, estimated fair values and unrealized gains and losses of investments classified as held-to-maturity [Abstract]
Amortized cost		78,790		62,302
Gross unrealized gains		107		49
Gross unrealized losses		180		209
Fair value		78,717		62,142
Allowance for credit losses		$ 450		$ 393		$ 0

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