Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Debt and Held-to-Maturity Securities (Details) - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020
Available-for-Sale Debt and Other, Amortized Cost
Less than 1 year		$ 888
1-5 years		13,361
5-10 years		11,985
Over 10 years		9,556
Other securities		518
Amortized Cost		36,308	$ 34,982
Available-for-Sale Debt and Other, Fair Value
Less than 1 year		903
1-5 years		14,019
5-10 years		12,700
Over 10 years		9,730
Other securities		518
Fair Value	[1]	37,870	37,513
Held-to-Maturity, Amortized Cost
Less than 1 year		2
1-5 years		4
5-10 years		0
Over 10 years		2
Other securities		0
Amortized Cost		8	11
Held-to-Maturity, Fair Value
Less than 1 year		2
1-5 years		4
5-10 years		0
Over 10 years		2
Other securities		0
Fair Value		$ 8	$ 11

[1] Amortized cost of $36,308 and $34,982 at September 30, 2021 and December 31, 2020, respectively.