Investment Securities - Schedule of Amortized Cost and Fair Value by Contractual Maturity (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Amortized Cost
Within 1 year	$ 0
After 1 year through 5 years	0
After 5 years through 10 years	0
After 10 years	0
Subtotal	0
Government agency issued MBS and CMO	1,229
Total	1,229
Fair Value
Within 1 year	0
After 1 year through 5 years	0
After 5 years through 10 years	0
After 10 years	0
Subtotal	0
Government agency issued MBS and CMO	1,079
Fair Value	1,079	$ 1,083
Amortized Cost
Within 1 year	16
After 1 year through 5 years	93
After 5 years through 10 years	480
After 10 years	1,132
Subtotal	1,721
Government agency issued MBS and CMO	7,117
Securities available for sale, amortized cost	8,838	8,930
Fair Value
Within 1 year	16
After 1 year through 5 years	87
After 5 years through 10 years	456
After 10 years	1,018
Subtotal	1,577
Government agency issued MBS and CMO	6,525
Securities available-for-sale	$ 8,102	$ 7,896