Financial Instruments (Marketable Securities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Estimated Fair Value	$ 2,564	$ 2,671
Available-For-Sale Marketable Securities [Member]
Amortized Cost	2,515	2,621
Gross Unrealized Gains	5	5
Gross Unrealized (Losses)	(6)	(3)
Estimated Fair Value	2,514	2,623
Categories of Investments, Marketable Securities, Trading Securities [Member]
Estimated Fair Value	50	48
Current Assets-Marketable Securities [Member]
Estimated Fair Value	2,513	2,622
Noncurrent Assets-Other [Member]
Estimated Fair Value	51	49
Corporate And Asset Backed Debt Securities [Member] | Available-For-Sale Marketable Securities [Member]
Amortized Cost	1,353	1,618
Gross Unrealized Gains	2	4
Gross Unrealized (Losses)	(5)	(2)
Estimated Fair Value	1,350	1,620
Foreign Government Debt Securities [Member] | Available-For-Sale Marketable Securities [Member]
Amortized Cost	745	523
Gross Unrealized Gains	3	1
Gross Unrealized (Losses)	(1)	(1)
Estimated Fair Value	747	523
US Government Agencies Debt Securities [Member] | Available-For-Sale Marketable Securities [Member]
Amortized Cost	241	314
Estimated Fair Value	241	314
Certificates Of Deposit [Member] | Available-For-Sale Marketable Securities [Member]
Amortized Cost	36	71
Estimated Fair Value	36	71
Other [Member] | Available-For-Sale Marketable Securities [Member]
Amortized Cost	140	95
Estimated Fair Value	$ 140	$ 95