Fair Value Measurements (Details) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Fixed Rate Debt:
Fixed Rate debt - Carrying amount	$ 2,873	$ 2,691
Fixed Rate debt - Fair value	3,018	2,791
Variable Rate Debt:
Variable Rate debt - Carrying amount	2,151	1,798
Variable Rate debt - Fair value	2,085	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	13	26
Total Assets at Fair Value	57	64
Liabilities:
Foreign Exchange Contracts	23	17
Total Liabilities at Fair Value	23	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	11	25
Total Assets at Fair Value	11	25
Liabilities:
Foreign Exchange Contracts	23	17
Total Liabilities at Fair Value	23	17
Significant Unobservable Inputs, Level 3 [Member]
Assets:
Investments	0	0
Foreign Exchange Contracts	2	1
Total Assets at Fair Value	2	1
Liabilities:
Foreign Exchange Contracts	0	0
Total Liabilities at Fair Value	$ 0	$ 0