Investment Securities - Schedule Of Amortized Cost And Fair Value By Contractual Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Available-for-sale, Amortized Cost [Abstract]
Within 1 year	$ 756
After 1 year through 5 years	160
After 5 years through 10 years	184
After 10 years	670
Subtotal, Amortized Cost	1,770
Government agency issued MBS and CMO	6,102
Securities available for sale, amortized cost	7,872
Available-for-sale, Fair Value [Abstract]
Within 1 year	758
After 1 year through 5 years	162
After 5 years through 10 years	192
After 10 years	717
Subtotal, Fair Value	1,829
Government agency issued MBS and CMO	6,218
Securities available for sale, fair value	$ 8,047	$ 4,445