Investment Securities (Summary Of Investment Securities Available-For-Sale In Unrealized Loss Positions) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Unrealized loss position, Impaired Less than 12 months, Fair Value	$ 0		$ 337
Unrealized loss position, Impaired Less than 12 months, Unrealized Losses	0		2
Unrealized loss position, Impaired 12 months or more, Fair Value	228		345
Unrealized loss position, Impaired 12 months or more, Unrealized Losses	9		19
Impaired, Total Fair Value	228		682
Impaired, Total Unrealized Losses	9		21
Residential Mortgage-Backed Securities [Member]
Unrealized loss position, Impaired Less than 12 months, Fair Value			249	[1]
Unrealized loss position, Impaired Less than 12 months, Unrealized Losses			1	[1]
Unrealized loss position, Impaired 12 months or more, Fair Value			0	[1]
Unrealized loss position, Impaired 12 months or more, Unrealized Losses			0	[1]
Impaired, Total Fair Value			249	[1]
Impaired, Total Unrealized Losses			1	[1]
State And Municipal Securities [Member]
Unrealized loss position, Impaired Less than 12 months, Fair Value	0	[2]	0	[2]
Unrealized loss position, Impaired Less than 12 months, Unrealized Losses	0	[2]	0	[2]
Unrealized loss position, Impaired 12 months or more, Fair Value	23	[2]	24	[2]
Unrealized loss position, Impaired 12 months or more, Unrealized Losses	5	[2]	5	[2]
Impaired, Total Fair Value	23	[2]	24	[2]
Impaired, Total Unrealized Losses	5	[2]	5	[2]
Auction-Rate Debt Securities [Member]
Unrealized loss position, Impaired Less than 12 months, Fair Value	0		0
Unrealized loss position, Impaired Less than 12 months, Unrealized Losses	0		0
Unrealized loss position, Impaired 12 months or more, Fair Value	1		1
Unrealized loss position, Impaired 12 months or more, Unrealized Losses	0	[3]	0	[3]
Impaired, Total Fair Value	1		1
Impaired, Total Unrealized Losses	0	[3]	0	[3]
Auction-Rate Preferred Securities [Member]
Unrealized loss position, Impaired Less than 12 months, Fair Value	0		88
Unrealized loss position, Impaired Less than 12 months, Unrealized Losses	0		1
Unrealized loss position, Impaired 12 months or more, Fair Value	204		320
Unrealized loss position, Impaired 12 months or more, Unrealized Losses	4		14
Impaired, Total Fair Value	204		408
Impaired, Total Unrealized Losses	$ 4		$ 15

[1] Residential mortgage-backed securities 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.