Fair Value Measurements (Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Marketable securities, at fair value
Marketable securities, at fair value	$ 63		$ 64
Derivatives not designated as hedging instruments
Interest rate swaps	(23)		(26)
Derivatives designated as cash flow hedging instruments
Interest rate swaps	(23)		(26)
Interest rate swaps	(9)		(13)
Mutual Funds [Member]
Marketable securities, at fair value
Marketable securities, at fair value	63		64
Fair Value, Measurements, Recurring [Member]
Derivatives designated as cash flow hedging instruments
Total assets	69		73
Total liabilities	(32)		(39)
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Derivatives designated as cash flow hedging instruments
Total assets	63		64
Total liabilities	0		0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Derivatives designated as cash flow hedging instruments
Total assets	6		9
Total liabilities	(32)		(39)
Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Marketable securities, at fair value
Marketable securities, at fair value	63		64
Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Marketable securities, at fair value
Marketable securities, at fair value	63		64
Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Marketable securities, at fair value
Marketable securities, at fair value	0		0
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivatives not designated as hedging instruments
Interest rate swaps	(16)	[1]	(21)	[1]
Derivatives designated as cash flow hedging instruments
Interest rate swaps	3	[2]
Interest rate swaps	(16)	[1]	(21)	[1]
Interest rate swaps	(9)	[3]	(13)	[3]
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]
Derivatives not designated as hedging instruments
Interest rate swaps	0	[1]	0	[1]
Derivatives designated as cash flow hedging instruments
Interest rate swaps	0	[2]
Interest rate swaps	0	[1]	0	[1]
Interest rate swaps	0	[3]	0	[3]
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Significant Other Observable Inputs (Level 2) [Member]
Derivatives not designated as hedging instruments
Interest rate swaps	(16)	[1]	(21)	[1]
Derivatives designated as cash flow hedging instruments
Interest rate swaps	3	[2]
Interest rate swaps	(16)	[1]	(21)	[1]
Interest rate swaps	(9)	[3]	(13)	[3]
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivatives not designated as hedging instruments
Interest rate swaps	0	[1]	(2)	[1]
Derivatives designated as cash flow hedging instruments
Interest rate swaps	0	[1]	(2)	[1]
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]
Derivatives not designated as hedging instruments
Interest rate swaps	0	[1]		[1]
Derivatives designated as cash flow hedging instruments
Interest rate swaps	0	[1]		[1]
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Significant Other Observable Inputs (Level 2) [Member]
Derivatives not designated as hedging instruments
Interest rate swaps	0	[1]	(2)	[1]
Derivatives designated as cash flow hedging instruments
Interest rate swaps	0	[1]	(2)	[1]
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Foreign Currency Forwards and Swaps [Member]
Derivatives not designated as hedging instruments
Foreign currency forwards and swaps	3	[4]	9	[4]
Foreign currency forwards and swaps	(7)	[1]	(3)	[1]
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]
Derivatives not designated as hedging instruments
Foreign currency forwards and swaps	0	[4]	0	[4]
Foreign currency forwards and swaps	0	[1]	0	[1]
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Foreign Currency Forwards and Swaps [Member] | Significant Other Observable Inputs (Level 2) [Member]
Derivatives not designated as hedging instruments
Foreign currency forwards and swaps	3	[4]	9	[4]
Foreign currency forwards and swaps	$ (7)	[1]	$ (3)	[1]

[1] Included in current Other liabilities in the unaudited consolidated balance sheets.

[2] Included in noncurrent Other assets in the unaudited consolidated balance sheets.

[3] Included in noncurrent Other liabilities in the unaudited consolidated balance sheets.

[4] Included in current Other assets in the unaudited consolidated balance sheets.