Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Debt and Held-to-Maturity Securities (Details) - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Available-for-Sale Debt and Other, Amortized Cost
Less than 1 year		$ 516
1-5 years		13,612
5-10 years		14,103
Over 10 years		5,931
Other securities		531
Amortized Cost		34,693	$ 34,966
Available-for-Sale Debt and Other, Fair Value
Less than 1 year		538
1-5 years		14,538
5-10 years		15,463
Over 10 years		6,355
Other securities		531
Fair Value	[1]	37,425	36,028
Held-to-Maturity, Amortized Cost
Less than 1 year		6
1-5 years		7
5-10 years		0
Over 10 years		2
Other securities		0
Amortized Cost	[2]	15	17
Held-to-Maturity, Fair Value
Less than 1 year		6
1-5 years		7
5-10 years		0
Over 10 years		2
Other securities		0
Fair Value		$ 15	$ 17

[1] Amortized cost of $34,693 and $34,966 at September 30, 2020 and December 31, 2019, respectively.

[2] Fair value of $15 and $17 at September 30, 2020 and December 31, 2019, respectively.