Investment Securities - Schedule Of Amortized Cost And Fair Value By Contractual Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Available-for-Sale, Amortized Cost
Within 1 year	$ 758
After 1 year through 5 years	146
After 5 years through 10 years	345
After 10 years	601
Subtotal	1,850
Government agency issued MBS and CMO	6,472
Securities available for sale, amortized cost	8,322
Available-for-Sale, Fair Value
Within 1 year	759
After 1 year through 5 years	148
After 5 years through 10 years	348
After 10 years	617
Subtotal	1,872
Government agency issued MBS and CMO	6,479
Securities available-for-sale	$ 8,351	$ 8,047