Investment Securities (Summary Of Investment Securities In Unrealized Loss Positions) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Document Period End Date		Dec. 31, 2019
Temporarily Impaired Less than 12 Months, Fair Value		$ 1,494	$ 1,008
Temporarily Impaired, Less than 12 Months, Unrealized Losses		7	9
Temporarily Impaired 12 Months or more, Fair Value		1,906	7,869
Temporarily Impaired, 12 Months or more, Unrealized Losses		21	207
Temporarily Impaired Total, Fair Value		3,400	8,877
Temporarily Impaired Total, Unrealized Losses		28	216
U.S. Treasury and other U.S. government agency securities
Temporarily Impaired Less than 12 Months, Fair Value			0
Temporarily Impaired, Less than 12 Months, Unrealized Losses			0
Temporarily Impaired 12 Months or more, Fair Value			1,457
Temporarily Impaired, 12 Months or more, Unrealized Losses			19
Temporarily Impaired Total, Fair Value			1,457
Temporarily Impaired Total, Unrealized Losses			19
Residential mortgage-backed securities
Temporarily Impaired Less than 12 Months, Fair Value	[1]	1,494	1,008
Temporarily Impaired, Less than 12 Months, Unrealized Losses	[1]	7	9
Temporarily Impaired 12 Months or more, Fair Value	[1]	1,906	6,412
Temporarily Impaired, 12 Months or more, Unrealized Losses	[1]	21	188
Temporarily Impaired Total, Fair Value	[1]	3,400	7,420
Temporarily Impaired Total, Unrealized Losses	[1]	$ 28	$ 197

[1] Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.