Investment Securities - Amortized Cost and Estimated Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Due within one year	$ 279
Due from one to five years	380
Due from five to ten years	1,561
Due after ten years	8,315
Amortized Cost	10,535
Mortgage-Related Debt Securities:
Debt Securities, Available-for-sale [Line Items]
Due within one year	82
Due from one to five years	92
Due from five to ten years	305
Due after ten years	8,554
Amortized Cost	9,033	$ 7,035
U.S. Government agency and GSE obligations
Debt Securities, Available-for-sale [Line Items]
Due within one year	150
Due from one to five years	0
Due from five to ten years	1,502
Due after ten years	0
Amortized Cost	1,652
US States and Political Subdivisions Debt Securities
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 Securities
Debt Securities, Available-for-sale [Line Items]
Due within one year	50
Due from one to five years	306
Due from five to ten years	104
Due after ten years	305
Amortized Cost	$ 765