Debt Securities - Maturity Schedule (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Available-for-Sale, Amortized Cost
Due within one year	$ 11,544
Due after one year through five years	846,883
Due after five years through ten years	33,140
Due after ten years	38,561
Total before mortgage-backed securities	930,128
Mortgage-backed securities	4,194,472
Amortized Cost	5,124,600	$ 5,283,253
Available-for-Sale, Fair Value
Due within one year	11,527
Due after one year through five years	793,437
Due after five years through ten years	32,114
Due after ten years	35,953
Total before mortgage-backed securities	873,031
Mortgage-backed securities	3,756,042
Debt securities, available-for-sale	4,629,073	4,785,719
Held-to-Maturity, Amortized Cost
Due within one year	5,212
Due after one year through five years	934,210
Due after five years through ten years	181,452
Due after ten years	1,375,468
Total before mortgage-backed securities	2,496,342
Mortgage-backed securities	955,241
Amortized Cost	3,451,583	3,502,411
Held-to-Maturity, Fair Value
Due within one year	5,194
Due after one year through five years	860,793
Due after five years through ten years	173,245
Due after ten years	1,180,930
Total before mortgage-backed securities	2,220,162
Mortgage-backed securities	871,032
Total	$ 3,091,194	$ 3,180,194