Available-For-Sale Investments (Fair Value And Gross Unrealized Losses Of Investments By Length Of Time In Continuous Unrealized Loss Position) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2011		Dec. 31, 2010
Asset-Backed Securities [Member]
Schedule Of Available-For-Sale Securities [Line Items]
Number of securities in a loss position	22		22
12 months or greater, Fair value	$ 38		$ 45
12 months or greater, Unrealized losses	(21)	[1]	(20)	[1]
Total, fair value	38		45
Total, unrealized losses	(21)		(20)
Long-Term Investments [Member]
Schedule Of Available-For-Sale Securities [Line Items]
Number of securities in a loss position	22		22
12 months or greater, Fair value	38		45
12 months or greater, Unrealized losses	(21)	[1]	(20)	[1]
Total, fair value	38		45
Total, unrealized losses	$ (21)		$ (20)

[1] Unrealized losses in securities less than 12 months were not significant.