Fair Value Measurements Fair Value of Derivatives by Balance Sheet Location (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Mar. 31, 2011	Dec. 31, 2010
Derivatives Fair Value [Line Items]
Maximum maturity of outstanding cash flow hedges, in months			36 months
Gain (loss) recognized in earnings for previously terminated interest rate swaps	$ 0		$ 0
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			0
Gain related to ineffective portion of hedging relationships	5,000,000	0	5,000,000	0
Unamortized losses on senior notes	4,000,000		4,000,000			5,000,000
Notional Amount of Interest Rate Fair Value Hedge Derivatives					850,000,000
Proceeds related to termination of interest rate swap contracts	80,000,000
Increase (Decrease) in Accrued Interest Receivable, Net	5,000,000
Principal amount of debt hedged by interest rate derivative contract	850,000,000		850,000,000
Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge	74,000,000		74,000,000
Notional Amount of Interest Rate Derivatives	0		0			0
Unamortized gains on senior notes	2,000,000		2,000,000			2,000,000
Unrealized gain on interest rate cash flow hedges, pretax, AOCI	7,000,000		7,000,000			8,000,000
Derivative Assets	83,000,000		83,000,000			82,000,000
Derivative Liabilities	161,000,000		161,000,000			189,000,000
Gain (Loss) in AOCI for effective portion of previously terminated interest rate contracts	4,000,000		4,000,000			5,000,000
Designated as Hedging Instrument [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments in Hedges, Assets, at Fair Value	42,000,000		42,000,000			59,000,000
Derivative Instruments in Hedges, Liabilities, at Fair Value	143,000,000		143,000,000			158,000,000
Designated as Hedging Instrument [Member] | Prepaid And Other Current Assets [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments in Hedges, Assets, at Fair Value	25,000,000		25,000,000			32,000,000
Designated as Hedging Instrument [Member] | Other Long Term Assets [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments in Hedges, Assets, at Fair Value	17,000,000		17,000,000			27,000,000
Designated as Hedging Instrument [Member] | Other current liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments in Hedges, Liabilities, at Fair Value	80,000,000		80,000,000			87,000,000
Designated as Hedging Instrument [Member] | Other Long Term Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments in Hedges, Liabilities, at Fair Value	63,000,000		63,000,000			71,000,000
Not Designated as Hedging Instrument [Member] | Prepaid And Other Current Assets [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	41,000,000		41,000,000			23,000,000
Not Designated as Hedging Instrument [Member] | Other current liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	$ 18,000,000		$ 18,000,000			$ 31,000,000