Fair Value Measurements (Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities, at fair value	$ 60	$ 64
Interest rate swaps	(17)	(26)
Interest rate swaps	(11)	(13)
Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities, at fair value	60	64
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	62	73
Total liabilities	(28)	(39)
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	60	64
Total liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	2	9
Total liabilities	(28)	(39)
Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities, at fair value	60	64
Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities, at fair value	60	64
Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps	0
Interest rate swaps	(14)	(21)
Interest rate swaps	(11)	(13)
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps	0
Interest rate swaps	0	0
Interest rate swaps	0	0
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps	0
Interest rate swaps	(14)	(21)
Interest rate swaps	(11)	(13)
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps	0	(2)
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps	0	0
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps	0	(2)
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Foreign Currency Forwards and Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency forwards and swaps	2	9
Foreign currency forwards and swaps	(3)	(3)
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Foreign Currency Forwards and Swaps [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency forwards and swaps	0	0
Foreign currency forwards and swaps	0	0
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Foreign Currency Forwards and Swaps [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency forwards and swaps	2	9
Foreign currency forwards and swaps	$ (3)	$ (3)