Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Debt and Held-to-Maturity Securities (Details) - USD ($) $ in Millions		Mar. 31, 2021	Dec. 31, 2020
Available-for-Sale Debt and Other, Amortized Cost
Less than 1 year		$ 1,037
1-5 years		15,093
5-10 years		12,529
Over 10 years		6,783
Other securities		521
Amortized Cost		35,963	$ 34,982
Available-for-Sale Debt and Other, Fair Value
Less than 1 year		1,064
1-5 years		15,887
5-10 years		13,287
Over 10 years		6,836
Other securities		521
Fair Value	[1]	37,595	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	[2]	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		$ 10	$ 11

[1] Amortized cost of $35,963 and $34,982 at March 31, 2021 and December 31, 2020, respectively.

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