Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Fixed Rate Debt:
Carrying amount - liability	$ 3,004	$ 2,843
Fair value - liability	3,105	2,891
Variable Rate Debt:
Carrying amount - liability	2,307	2,071
Fair value - liability	2,274	2,029
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	49	44
Foreign Exchange Contracts	13	37
Total Assets at Fair Value	62	81
Liabilities:
Foreign Exchange Contracts	15	6
Total Liabilities at Fair Value	15	6
Quoted Prices in Active Markets for Identical Assets/Liabilities, Level 1 [Member]
Assets:
Investments	49	44
Foreign Exchange Contracts	0	0
Total Assets at Fair Value	49	44
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	13	37
Total Assets at Fair Value	13	37
Liabilities:
Foreign Exchange Contracts	15	5
Total Liabilities at Fair Value	15	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
Total Liabilities at Fair Value	$ 0	$ 1