Fair Value Measurements (Fair Value, Measurement Inputs, Disclosure) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	$ 1,520	[1]	$ 1,752	[1]
Other assets	157		153
Current Assets [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	9	[2]	5	[2]
Current Assets [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	9	[2]	5	[2]
Non-Current Assets [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	1	[2]
Other assets	38		45
Non-Current Assets [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	1	[2]
Other assets	38		45
Current Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivatives, liabilities	170	[2]	155	[2]
Current Liabilities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivatives, liabilities	170	[2]	155	[2]
Non-Current Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivatives, liabilities	25	[2]	45	[2]
Non-Current Liabilities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivatives, liabilities	25	[2]	45	[2]
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	1,512	[1]	1,737	[1]
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	$ 8	[1]	$ 15	[1]

[1] Short-term investments are measured using observable quoted prices for similar assets.

[2] Derivative assets and liabilities include foreign exchange contracts which are measured using observable quoted prices for similar assets and liabilities.