Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fixed Rate Debt:
Carrying amount - liability	$ 3,128	$ 2,843
Fair value - liability	3,378	2,891
Variable Rate Debt:
Carrying amount - liability	1,798	2,071
Fair value - liability	1,808	2,029
Total Carrying Value in the Consolidated Balance Sheet [Member]
Assets:
Investments	45	44
Foreign Exchange Contracts	2	37
Total Assets at Fair Value	47	81
Liabilities:
Foreign Exchange Contracts	29	6
Other Liabilities, Fair Value Disclosure	3	0
Total Liabilities at Fair Value	32	6
Quoted Prices in Active Markets for Identical Assets/Liabilities, Level 1 [Member]
Assets:
Investments	45	44
Foreign Exchange Contracts	0	0
Total Assets at Fair Value	45	44
Liabilities:
Foreign Exchange Contracts	0	0
Other Liabilities, Fair Value Disclosure	0	0
Total Liabilities at Fair Value	0	0
Significant Other Observable Inputs, Level 2 [Member]
Assets:
Investments	0	0
Foreign Exchange Contracts	2	37
Total Assets at Fair Value	2	37
Liabilities:
Foreign Exchange Contracts	29	5
Other Liabilities, Fair Value Disclosure	3	0
Total Liabilities at Fair Value	32	5
Significant Unobservable Inputs, Level 3 [Member]
Assets:
Investments	0	0
Foreign Exchange Contracts	0	0
Total Assets at Fair Value	0	0
Liabilities:
Foreign Exchange Contracts	0	1
Other Liabilities, Fair Value Disclosure	0	0
Total Liabilities at Fair Value	$ 0	$ 1