Investment Securities - Schedule of Amortized Cost and Fair Value by Contractual Maturity (Details) - USD ($) $ in Millions	Mar. 31, 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	1,258
Total	1,258
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	1,092
Fair Value	1,092	$ 1,083
Amortized Cost
Within 1 year	11
After 1 year through 5 years	98
After 5 years through 10 years	265
After 10 years	1,207
Subtotal	1,581
Government agency issued MBS and CMO	7,375
Securities available for sale, amortized cost	8,956
Fair Value
Within 1 year	11
After 1 year through 5 years	92
After 5 years through 10 years	237
After 10 years	1,072
Subtotal	1,412
Government agency issued MBS and CMO	6,663
Securities available-for-sale	$ 8,075	$ 7,896