Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Debt and Held-to-Maturity Securities (Details) - USD ($) $ in Millions		Jun. 30, 2021	Dec. 31, 2020
Available-for-Sale Debt and Other, Amortized Cost
Less than 1 year		$ 886
1-5 years		14,074
5-10 years		11,482
Over 10 years		9,119
Other securities		520
Amortized Cost		36,081	$ 34,982
Available-for-Sale Debt and Other, Fair Value
Less than 1 year		907
1-5 years		14,825
5-10 years		12,349
Over 10 years		9,411
Other securities		520
Fair Value	[1]	38,012	37,513
Held-to-Maturity, Amortized Cost
Less than 1 year		4
1-5 years		4
5-10 years		0
Over 10 years		2
Other securities		0
Amortized Cost		10	11
Held-to-Maturity, Fair Value
Less than 1 year		4
1-5 years		4
5-10 years		0
Over 10 years		2
Other securities		0
Fair Value	[2]	$ 10	$ 11

[1] Amortized cost of $36,081 and $34,982 at June 30, 2021 and December 31, 2020, respectively.

[2] Fair value of $10 and $11 at June 30, 2021 and December 31, 2020, respectively.