Available-For-Sale Securities (Value Of Securities That Have Been In An Unrealized Loss Position For Less Than And Greater Than 12 Months) (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Unrealized Loss Position Greater Than 12 Months [Member] | Total Available-For-Sale Securities Debt Securities [Member]
Estimated Fair Value	$ 7	$ 9
Gross Unrealized Losses	(1)	(1)
Unrealized Loss Position Greater Than 12 Months [Member] | Debt Securities Total [Member]
Estimated Fair Value	7	9
Gross Unrealized Losses	(1)	(1)
Unrealized Loss Position Greater Than 12 Months [Member] | Other Debt Securities [Member]
Estimated Fair Value	5	8
Gross Unrealized Losses	(1)	(1)
Unrealized Loss Position Greater Than 12 Months [Member] | US States And Political Subdivisions Debt Securities [Member]
Estimated Fair Value	2	1
Gross Unrealized Losses	0	0
Unrealized Loss Position Greater Than 12 Months [Member] | Equity Securities [Member]
Estimated Fair Value	0	0
Gross Unrealized Losses	0	0
Unrealized Loss Position Greater Than 12 Months [Member] | Other Securities [Member]
Estimated Fair Value	0	0
Gross Unrealized Losses	0	0
Unrealized Loss Position Less Than 12 Months [Member] | Total Available-For-Sale Securities Debt Securities [Member]
Estimated Fair Value	281	226
Gross Unrealized Losses	(9)	(8)
Unrealized Loss Position Less Than 12 Months [Member] | Debt Securities Total [Member]
Estimated Fair Value	153	171
Gross Unrealized Losses	(3)	(5)
Unrealized Loss Position Less Than 12 Months [Member] | Other Debt Securities [Member]
Estimated Fair Value	50	65
Gross Unrealized Losses	(1)	(1)
Unrealized Loss Position Less Than 12 Months [Member] | US States And Political Subdivisions Debt Securities [Member]
Estimated Fair Value	103	106
Gross Unrealized Losses	(2)	(4)
Unrealized Loss Position Less Than 12 Months [Member] | Equity Securities [Member]
Estimated Fair Value	127	55
Gross Unrealized Losses	(6)	(3)
Unrealized Loss Position Less Than 12 Months [Member] | Other Securities [Member]
Estimated Fair Value	1	0
Gross Unrealized Losses	0	0
Total Available-For-Sale Securities Debt Securities [Member]
Estimated Fair Value	168	160
Gross Unrealized Losses	0	0
Debt Securities [Member]
Estimated Fair Value	148	142
Gross Unrealized Losses	0	0
Equity Securities [Member]
Estimated Fair Value	20	18
Gross Unrealized Losses	$ 0	$ 0