Financial Instruments and Risk Management (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 Debt_Instrument		Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Fair value of marketable securities	$ 398,000,000		$ 150,000,000
Foreign Currency Derivatives [Abstract]
Maximum term of currency derivative instruments (in years)	1 year
Notional amount of foreign exchange forward contracts and option contracts	324,000,000		268,000,000
Interest Rate Derivatives [Abstract]
Number of debt instruments with related interest rate swaps (debt instruments)	2
Notional amount	1,000,000,000
Floating rate basis	LIBOR-based
Weighted average floating rate (percentage)	3.30%
Aggregate fixed rate debt after effect of interest rate swaps	3,800,000,000
Aggregate floating rate debt after effect of interest rate swaps	1,000,000,000
Long-term Debt, Percentage Bearing Fixed Interest, Amount	4,800,000,000
Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Fair value of marketable securities	150,000,000		150,000,000
Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Fair value of marketable securities	248,000,000
Estimate of Fair Value, Fair Value Disclosure
Interest Rate Derivatives [Abstract]
Long-term debt	6,384,000,000		6,158,000,000
Estimate of Fair Value, Fair Value Disclosure | Level 1
Interest Rate Derivatives [Abstract]
Long-term debt	1,112,000,000		3,555,000,000
Estimate of Fair Value, Fair Value Disclosure | Level 2
Interest Rate Derivatives [Abstract]
Long-term debt	5,272,000,000		2,603,000,000
Carrying (Reported) Amount, Fair Value Disclosure
Interest Rate Derivatives [Abstract]
Long-term debt	4,820,000,000		4,820,000,000
Other current assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Available-for-sale securities, current	120,000,000
Other assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Available-for-sale securities, noncurrent	128,000,000
US treasuries
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Fair value of marketable securities	150,000,000	[1]	150,000,000	[1]
US treasuries | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Fair value of marketable securities	150,000,000	[1]	150,000,000	[1]
US treasuries | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Fair value of marketable securities	0	[1]
Other
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Fair value of marketable securities	248,000,000	[2]	0	[2]
Other | Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Fair value of marketable securities	0	[2]	0	[2]
Other | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Fair value of marketable securities	$ 248,000,000	[2]

[1] These securities are classified as "Other current assets" in our consolidated balance sheets.

[2] Of these securities, $120 million are classified as “Other current assets” and $128 million are classified as “Other assets” in our consolidated balance sheets. These securities consist primarily of municipal bonds, corporate bonds, and other debt instruments.