Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Debt and Held-to-Maturity Securities (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Available-for-Sale Debt and Other, Amortized Cost
Less than 1 year		$ 633
1-5 years		15,881
5-10 years		12,214
Over 10 years		5,730
Other securities		524
Amortized Cost		34,982	$ 34,966
Available-for-Sale Debt and Other, Fair Value
Less than 1 year		648
1-5 years		16,959
5-10 years		13,385
Over 10 years		5,997
Other securities		524
Fair Value	[1]	37,513	36,028
Held-to-Maturity, Amortized Cost
Less than 1 year		2
1-5 years		7
5-10 years		0
Over 10 years		2
Other securities		0
Amortized Cost	[2]	11	17
Held-to-Maturity, Fair Value
Less than 1 year		2
1-5 years		7
5-10 years		0
Over 10 years		2
Other securities		0
Fair Value		$ 11	$ 17

[1] Amortized cost of $34,982 and $34,966 at December 31, 2020 and 2019, respectively.

[2] Fair value of $11 and $17 at December 31, 2020 and 2019, respectively.