Investment Securities - Amortized Cost and Estimated Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Due within one year	$ 130
Due from one to five years	334
Due from five to ten years	1,535
Due after ten years	8,403
Amortized Cost	10,402
Mortgage- Related Securities
Debt Securities, Available-for-sale [Line Items]
Due within one year	81
Due from one to five years	113
Due from five to ten years	290
Due after ten years	8,671
Amortized Cost	9,155	$ 7,035
U.S. Government and GSE Obligations
Debt Securities, Available-for-sale [Line Items]
Due within one year	0
Due from one to five years	0
Due from five to ten years	1,502
Due after ten years	0
Amortized Cost	1,502
State, County, and Municipal
Debt Securities, Available-for-sale [Line Items]
Due within one year	0
Due from one to five years	5
Due from five to ten years	0
Due after ten years	0
Amortized Cost	5
Other Debt Obligations
Debt Securities, Available-for-sale [Line Items]
Due within one year	50
Due from one to five years	222
Due from five to ten years	84
Due after ten years	277
Amortized Cost	$ 633