Investment Securities (Summary Of Investment Securities In Unrealized Loss Positions) (Details) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Temporarily Impaired Less than 12 months, Fair Value		$ 1,468	$ 1,008
Temporarily Impaired Less than 12 Months, Unrealized Losses		3	9
Temporarily Impaired 12 months or more, Fair Value		6,757	7,869
Temporarily Impaired 12 Months or more, Unrealized Losses		115	207
Temporarily Impaired Total, Fair Value		8,225	8,877
Temporarily Impaired Total, Unrealized Losses		118	216
U.S. Treasury and other U.S. government agency securities
Temporarily Impaired Less than 12 months, Fair Value		1,100	0
Temporarily Impaired Less than 12 Months, Unrealized Losses		3	0
Temporarily Impaired 12 months or more, Fair Value		378	1,457
Temporarily Impaired 12 Months or more, Unrealized Losses		2	19
Temporarily Impaired Total, Fair Value		1,478	1,457
Temporarily Impaired Total, Unrealized Losses		5	19
Residential mortgage-backed securities
Temporarily Impaired Less than 12 months, Fair Value	[1]	368	1,008
Temporarily Impaired Less than 12 Months, Unrealized Losses	[1]	0	9
Temporarily Impaired 12 months or more, Fair Value	[1]	6,379	6,412
Temporarily Impaired 12 Months or more, Unrealized Losses	[1]	113	188
Temporarily Impaired Total, Fair Value	[1]	6,747	7,420
Temporarily Impaired Total, Unrealized Losses	[1]	$ 113	$ 197

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