Investment Securities (Summary Of Investment Securities In Unrealized Loss Positions) (Details) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Temporarily Impaired Less than 12 months, Fair Value		$ 6,132	$ 6,572
Temporarily Impaired Less than 12 Months, Unrealized Losses		136	48
Temporarily Impaired 12 months or more, Fair Value		4,545	4,052
Temporarily Impaired 12 Months or more, Unrealized Losses		235	127
Temporarily Impaired Total, Fair Value		10,677	10,624
Temporarily Impaired Total, Unrealized Losses		371	175
U.S. Treasury and other U.S. government agency securities
Temporarily Impaired Less than 12 months, Fair Value		1,852	2,727
Temporarily Impaired Less than 12 Months, Unrealized Losses		30	16
Temporarily Impaired 12 months or more, Fair Value		182	0
Temporarily Impaired 12 Months or more, Unrealized Losses		2	0
Temporarily Impaired Total, Fair Value		2,034	2,727
Temporarily Impaired Total, Unrealized Losses		32	16
Residential mortgage-backed securities
Temporarily Impaired Less than 12 months, Fair Value	[1]	4,280	3,845
Temporarily Impaired Less than 12 Months, Unrealized Losses	[1]	106	32
Temporarily Impaired 12 months or more, Fair Value	[1]	4,363	4,003
Temporarily Impaired 12 Months or more, Unrealized Losses	[1]	233	125
Temporarily Impaired Total, Fair Value	[1]	8,643	7,848
Temporarily Impaired Total, Unrealized Losses	[1]	$ 339	157
State and municipal securities
Temporarily Impaired Less than 12 months, Fair Value	[2]		0
Temporarily Impaired Less than 12 Months, Unrealized Losses	[2]		0
Temporarily Impaired 12 months or more, Fair Value	[2]		5
Temporarily Impaired 12 Months or more, Unrealized Losses	[2],[3]		0
Temporarily Impaired Total, Fair Value	[2]		5
Temporarily Impaired Total, Unrealized Losses	[2],[3]		0
Equity and other non-debt securities
Temporarily Impaired Less than 12 months, Fair Value	[2]		0
Temporarily Impaired Less than 12 Months, Unrealized Losses	[2]		0
Temporarily Impaired 12 months or more, Fair Value	[2]		44
Temporarily Impaired 12 Months or more, Unrealized Losses	[2]		2
Temporarily Impaired Total, Fair Value	[2]		44
Temporarily Impaired Total, Unrealized Losses	[2]		$ 2

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

[2] Primarily auction-rate securities.

[3] Unrealized losses less than $0.5 million.