Investment Securities - Amortized Cost and Estimated Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Due within one year	$ 446
Due from one to five years	560
Due from five to ten years	1,597
Due after ten years	6,542
Amortized Cost	9,145
Mortgage- Related Securities
Debt Securities, Available-for-sale [Line Items]
Due within one year	0
Due from one to five years	178
Due from five to ten years	316
Due after ten years	6,541
Amortized Cost	7,035	$ 5,242
U.S. Government and GSE Obligations
Debt Securities, Available-for-sale [Line Items]
Due within one year	448
Due from one to five years	50
Due from five to ten years	1,502
Due after ten years	96
Amortized Cost	2,096
State, County, and Municipal
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	6
Due after ten years	0
Amortized Cost	6
Other Debt Obligations
Debt Securities, Available-for-sale [Line Items]
Due within one year	0
Due from one to five years	353
Due from five to ten years	105
Due after ten years	345
Amortized Cost	$ 803