Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Debt and Held-to-Maturity Securities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Available-for-Sale Debt and Other, Amortized Cost
Due in 1 year or less	$ 984
Due after 1 year through 5 years	13,262
Due after 5 years through 10 years	11,951
Due after 10 years	10,225
Other securities	519
Amortized Cost	36,941	$ 34,982
Available-for-Sale Debt and Other, Fair Value
Due in 1 year or less	1,003
Due after 1 year through 5 years	13,756
Due after 5 years through 10 years	12,466
Due after 10 years	10,366
Other securities	519
Fair Value	38,110	37,513
Held-to-Maturity, Amortized Cost
Due in 1 year or less	3
Due after 1 year through 5 years	3
Due after 5 years through 10 years	0
Due after 10 years	2
Other securities	0
Amortized Cost	8	11
Held-to-Maturity, Fair Value
Due in 1 year or less	3
Due after 1 year through 5 years	3
Due after 5 years through 10 years	0
Due after 10 years	2
Other securities	0
Fair Value	$ 8	$ 11