Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Fixed Rate Debt:
Carrying amount - liability	$ 2,843	$ 2,691
Fair value - liability	2,891	2,791
Variable Rate Debt:
Carrying amount - liability	2,071	1,798
Fair value - liability	2,029	1,770
Fair Value Measurements (Textuals) [Abstract]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	Realized and unrealized gains and losses related to the embedded currency derivatives are included in Other Expense.
Fair Value, Foreign Currency Contracts, Valuation Techniques	The valuation of the embedded currency derivatives is based on an extrapolation of forward rates to the assumed expiration of the leases.
Total Carrying Value in the Consolidated Balance Sheet [Member]
Assets:
Investments	44	38
Foreign Exchange Contracts	37	26
Total Assets at Fair Value	81	64
Liabilities:
Foreign Exchange Contracts	6	17
Total Liabilities at Fair Value	6	17
Quoted Prices in Active Markets for Identical Assets/Liabilities, Level 1 [Member]
Assets:
Investments	44	38
Foreign Exchange Contracts	0	0
Total Assets at Fair Value	44	38
Liabilities:
Foreign Exchange Contracts	0	0
Total Liabilities at Fair Value	0	0
Significant Other Observable Inputs, Level 2 [Member]
Assets:
Investments	0	0
Foreign Exchange Contracts	37	25
Total Assets at Fair Value	37	25
Liabilities:
Foreign Exchange Contracts	5	17
Total Liabilities at Fair Value	5	17
Significant Unobservable Inputs, Level 3 [Member]
Assets:
Investments	0	0
Foreign Exchange Contracts	0	1
Total Assets at Fair Value	0	1
Liabilities:
Foreign Exchange Contracts	1	0
Total Liabilities at Fair Value	$ 1	$ 0