Investment Securities - Schedule of Amortized Cost and Fair Value by Contractual Maturity (Details) - USD ($) $ in Millions	Jun. 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	1,245
Total	1,245
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	1,083
Fair Value	1,083	$ 1,083
Amortized Cost
Within 1 year	15
After 1 year through 5 years	93
After 5 years through 10 years	318
After 10 years	1,173
Subtotal	1,599
Government agency issued MBS and CMO	7,327
Securities available for sale, amortized cost	8,926	8,930
Fair Value
Within 1 year	15
After 1 year through 5 years	88
After 5 years through 10 years	293
After 10 years	1,043
Subtotal	1,439
Government agency issued MBS and CMO	6,678
Securities available-for-sale	$ 8,117	$ 7,896