Investment Securities (Schedule Of Gross Unrealized Losses And Fair Values Of Securities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Less than 12 months, Fair Value	$ 625	$ 1,821
Less than 12 months, Gross Unrealized Losses	(11)	(44)
12 months or more, Fair Value	135	171
12 months or more, Gross Unrealized Losses	(6)	(18)
Total, Fair Value	760	1,992
Total, Gross Unrealized Losses	(17)	(62)
Debt Securities [Member] | Tax-Exempt Municipal Securities [Member]
Less than 12 months, Fair Value	53	1,168
Less than 12 months, Gross Unrealized Losses	0	(33)
12 months or more, Fair Value	48	98
12 months or more, Gross Unrealized Losses	(2)	(11)
Total, Fair Value	101	1,266
Total, Gross Unrealized Losses	(2)	(44)
Debt Securities [Member] | Residential Mortgage-Backed Securities [Member]
Less than 12 months, Fair Value	3	0
Less than 12 months, Gross Unrealized Losses	0	0
12 months or more, Fair Value	24	33
12 months or more, Gross Unrealized Losses	(2)	(3)
Total, Fair Value	27	33
Total, Gross Unrealized Losses	(2)	(3)
Debt Securities [Member] | Commercial Mortgage-Backed Securities [Member]
Less than 12 months, Fair Value	14	0
Less than 12 months, Gross Unrealized Losses	0	0
12 months or more, Fair Value	0	3
12 months or more, Gross Unrealized Losses	0	0
Total, Fair Value	14	3
Total, Gross Unrealized Losses	0	0
Debt Securities [Member] | Asset-Backed Securities [Member]
Less than 12 months, Fair Value	16	17
Less than 12 months, Gross Unrealized Losses	0	0
12 months or more, Fair Value	4	0
12 months or more, Gross Unrealized Losses	0	0
Total, Fair Value	20	17
Total, Gross Unrealized Losses	0	0
Debt Securities [Member] | Corporate Debt Securities [Member]
Less than 12 months, Fair Value	355	384
Less than 12 months, Gross Unrealized Losses	(10)	(10)
12 months or more, Fair Value	41	31
12 months or more, Gross Unrealized Losses	(1)	(4)
Total, Fair Value	396	415
Total, Gross Unrealized Losses	(11)	(14)
Debt Securities [Member] | U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | U.S. Treasury And Agency Obligations [Member]
Less than 12 months, Fair Value	117	142
Less than 12 months, Gross Unrealized Losses	0	0
12 months or more, Fair Value	0	0
12 months or more, Gross Unrealized Losses	0	0
Total, Fair Value	117	142
Total, Gross Unrealized Losses	0	0
Debt Securities [Member] | U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | Mortgage-Backed Securities [Member]
Less than 12 months, Fair Value	67	110
Less than 12 months, Gross Unrealized Losses	(1)	(1)
12 months or more, Fair Value	18	6
12 months or more, Gross Unrealized Losses	(1)	0
Total, Fair Value	85	116
Total, Gross Unrealized Losses	$ (2)	$ (1)