Investment Securities - Schedule Of Amortized Cost And Fair Value By Contractual Maturity (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Held-to-Maturity, Amortized Cost
Within 1 year	$ 0
After 1 year through 5 years	0
After 5 years through 10 years
After 10 years	0
Subtotal	0
Government agency issued MBS and CMO	304
Total	304
Held-to-Maturity, 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	303
Fair Value	303	$ 10
Available-for-Sale, Amortized Cost
Within 1 year	654
After 1 year through 5 years	152
After 5 years through 10 years	347
After 10 years	760
Subtotal	1,913
Government agency issued MBS and CMO	6,558
Securities available for sale, amortized cost	8,471
Available-for-Sale, Fair Value
Within 1 year	654
After 1 year through 5 years	153
After 5 years through 10 years	355
After 10 years	770
Subtotal	1,932
Government agency issued MBS and CMO	6,562
Securities available-for-sale	$ 8,494	$ 8,047