Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Debt and Held-to-Maturity Securities (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Available-for-Sale Debt and Other, Amortized Cost
Due in 1 year or less	$ 4,244
Due after 1 year through 5 years	15,415
Due after 5 years through 10 years	16,655
Due after 10 years	6,307
Other securities	824
Amortized Cost	43,445	$ 43,878
Available-for-Sale Debt and Other, Fair Value
Due in 1 year or less	4,232
Due after 1 year through 5 years	14,651
Due after 5 years through 10 years	14,620
Due after 10 years	5,420
Other securities	824
Fair Value	39,747	39,547
Held-to-Maturity, Amortized Cost
Due in 1 year or less	328
Due after 1 year through 5 years	3,023
Due after 5 years through 10 years	7,420
Due after 10 years	414
Other securities	0
Amortized Cost	11,185	11,278
Held-to-Maturity, Fair Value
Due in 1 year or less	328
Due after 1 year through 5 years	3,022
Due after 5 years through 10 years	7,307
Due after 10 years	415
Other securities	0
Fair Value	$ 11,072	$ 10,965