Financial Instruments (Unrealized Losses And Fair Value Of Investments With Unrealized Losses) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Less Than 12 months - Number of Investments	417	290
Less Than 12 months - Estimated Fair Value	$ 1,091	$ 1,076
Less Than 12 months - Gross Unrealized Losses	6	3
Total - Number of Investments	417	290
Total - Fair Value	1,091	1,076
Total - Unrealized Losses	6	3
Corporate And Asset Backed Debt Securities [Member]
Less Than 12 months - Number of Investments	266	216
Less Than 12 months - Estimated Fair Value	573	753
Less Than 12 months - Gross Unrealized Losses	5	2
Total - Number of Investments	266	216
Total - Fair Value	573	753
Total - Unrealized Losses	5	2
Foreign Government Debt Securities [Member]
Less Than 12 months - Number of Investments	58	42
Less Than 12 months - Estimated Fair Value	285	224
Less Than 12 months - Gross Unrealized Losses	1	1
Total - Number of Investments	58	42
Total - Fair Value	285	224
Total - Unrealized Losses	1	1
US Government Agencies Debt Securities [Member]
Less Than 12 months - Number of Investments	60	32
Less Than 12 months - Estimated Fair Value	145	99
Total - Number of Investments	60	32
Total - Fair Value	145	99
Other Debt Obligations [Member]
Less Than 12 months - Number of Investments	33
Less Than 12 months - Estimated Fair Value	88
Total - Number of Investments	33
Total - Fair Value	$ 88