Investment Securities - Schedule Of Amortized Cost And Fair Value By Contractual Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
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	1,311
Total	1,311
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	1,131
Fair Value	1,131	$ 1,161
Amortized Cost
Within 1 year	49
After 1 year through 5 years	129
After 5 years through 10 years	372
After 10 years	1,369
Subtotal	1,919
Government agency issued MBS and CMO	7,407
Securities available for sale, amortized cost	9,326
Fair Value
Within 1 year	48
After 1 year through 5 years	120
After 5 years through 10 years	339
After 10 years	1,205
Subtotal	1,712
Government agency issued MBS and CMO	6,436
Securities available-for-sale	$ 8,148	$ 8,391