Securities - Schedule of Book Values and Fair Values of Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Amortized Cost
Due within one year	$ 127,331
Due after one year but within five years	59,869
Due after five years but within ten years	78,130
Due after ten years	1,000
Mortgage-backed securities	2,355,736
Amortized Cost	2,622,066	$ 2,758,556
Fair Value
Due within one year	124,793
Due after one year but within five years	56,553
Due after five years but within ten years	63,691
Due after ten years	921
Mortgage-backed securities	1,854,448
Total securities	2,100,406	2,314,493
Amortized Cost
Due within one year	0
Due after one year but within five years	1,998
Due after five years but within ten years	122,111
Due after ten years	398,596
Mortgage-backed securities	12,755
Amortized Cost	535,460	541,700
Fair Value
Due within one year	0
Due after one year but within five years	1,727
Due after five years but within ten years	96,588
Due after ten years	300,332
Mortgage-backed securities	11,674
Total securities	$ 410,321	$ 432,528