Investment Securities (Proceeds and Gross Realized Gains And Losses from Sales of Securities Available for Sale) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021		Jun. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Proceeds	$ 3,037	$ 1	$ 9,642	[1]	$ 70	[1]
Gross realized gains	17	0	37		0
Gross realized losses	$ 13	$ 0	$ 23		$ 0

[1] Certain prior year amounts have been reclassified to conform to the current year presentation. See Note 1 for additional information.