Investment Securities - Schedule of Amortized Cost and Fair Value by Contractual Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
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	1,204
Total	1,204
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	1,056
Fair Value	1,056	$ 1,073
Amortized Cost
Within 1 year	16
After 1 year through 5 years	139
After 5 years through 10 years	705
After 10 years	1,103
Subtotal	1,963
Government agency issued MBS and CMO	6,878
Amortized Cost	8,841	8,841
Fair Value
Within 1 year	16
After 1 year through 5 years	127
After 5 years through 10 years	682
After 10 years	1,004
Subtotal	1,829
Government agency issued MBS and CMO	6,317
Securities available-for-sale	$ 8,146	$ 8,165