Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Debt and Held-to-Maturity Securities (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Available-for-Sale Debt and Other, Amortized Cost
Due in 1 year or less	$ 904
Due after 1 year through 5 years	18,452
Due after 5 years through 10 years	15,740
Due after 10 years	7,706
Other securities	794
Amortized Cost	43,596	$ 55,789
Available-for-Sale Debt and Other, Fair Value
Due in 1 year or less	875
Due after 1 year through 5 years	17,404
Due after 5 years through 10 years	13,343
Due after 10 years	6,570
Other securities	794
Fair Value	38,986	50,419
Held-to-Maturity, Amortized Cost
Due in 1 year or less	38
Due after 1 year through 5 years	2,930
Due after 5 years through 10 years	7,995
Due after 10 years	480
Other securities	0
Amortized Cost	11,443	2
Held-to-Maturity, Fair Value
Due in 1 year or less	38
Due after 1 year through 5 years	2,882
Due after 5 years through 10 years	7,787
Due after 10 years	480
Other securities	0
Fair Value	$ 11,187	$ 2