Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Debt and Held-to-Maturity Securities (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Available-for-Sale Debt and Other, Amortized Cost
Due in 1 year or less	$ 2,871
Due after 1 year through 5 years	13,192
Due after 5 years through 10 years	17,364
Due after 10 years	5,322
Other securities	868
Total	39,617	$ 43,878
Available-for-Sale Debt and Other, Fair Value
Due in 1 year or less	2,860
Due after 1 year through 5 years	12,567
Due after 5 years through 10 years	15,534
Due after 10 years	4,632
Other securities	868
Fair Value	36,461	39,547
Held-to-Maturity, Amortized Cost
Due in 1 year or less	605
Due after 1 year through 5 years	2,795
Due after 5 years through 10 years	7,765
Due after 10 years	333
Other securities	0
Amortized Cost	11,498	11,278
Held-to-Maturity, Fair Value
Due in 1 year or less	605
Due after 1 year through 5 years	2,820
Due after 5 years through 10 years	7,746
Due after 10 years	335
Other securities	0
Fair Value	$ 11,506	$ 10,965