Financial Instruments (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Fair Value of Derivative Instruments
Asset Derivatives	$ 12,700,000		$ 4,500,000
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0		0
Derivative Asset	12,700,000		4,500,000
Derivative, Collateral, Obligation to Return Securities	(1,700,000)		(1,500,000)
Derivative, Collateral, Obligation to Return Cash	0		0
Derivative Asset, Fair Value, Amount Offset Against Collateral	11,000,000		3,000,000
Liability Derivatives	14,200,000		5,500,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0		0
Derivative Liability	14,200,000		5,500,000
Derivative, Collateral, Right to Reclaim Securities	(1,700,000)		(1,500,000)
Derivative, Collateral, Right to Reclaim Cash	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	12,500,000		4,000,000
Amount of Gain or (Loss) Recognized in Income on Derivatives	0		8,500,000		0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	0
Unrealized holding gains (losses) on securities, (net of tax of 2013: $0; 2012: $0; and 2011: $0.1)	21,000,000		(300,000)		200,000
Balance at the end of period			0
Debt
Maximum initial maturity period of borrowings			90 days
Long Lived Assets
Asset Impairment Charges	(40,000,000)
Fair Value Inputs, Discount Rate	6.50%
Fair Value Assumptions, Expected Volatility Rate	40.00%
Gasoline swaps
Fair Value of Derivative Instruments
Asset Derivatives	1,800,000
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0
Derivative Asset	1,800,000
Derivative, Collateral, Obligation to Return Securities	(100,000)
Derivative, Collateral, Obligation to Return Cash	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	1,700,000
Liability Derivatives			100,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset			0
Derivative Liability			100,000
Derivative, Collateral, Right to Reclaim Securities			0
Derivative, Collateral, Right to Reclaim Cash			0
Derivative Liability, Fair Value, Amount Offset Against Collateral			100,000
Interest rate caps
Fair Value of Derivative Instruments
Asset Derivatives	9,100,000		900,000
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0		0
Derivative Asset	9,100,000		900,000
Derivative, Collateral, Obligation to Return Securities	0		0
Derivative, Collateral, Obligation to Return Cash	0		0
Derivative Asset, Fair Value, Amount Offset Against Collateral	9,100,000		900,000
Liability Derivatives	8,900,000		900,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0		0
Derivative Liability	8,900,000		900,000
Derivative, Collateral, Right to Reclaim Securities	0		0
Derivative, Collateral, Right to Reclaim Cash	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	8,900,000		900,000
Foreign exchange forward contracts
Fair Value of Derivative Instruments
Asset Derivatives	1,700,000		3,400,000
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0		0
Derivative Asset	1,700,000		3,400,000
Derivative, Collateral, Obligation to Return Securities	(1,500,000)		(1,300,000)
Derivative, Collateral, Obligation to Return Cash	0		0
Derivative Asset, Fair Value, Amount Offset Against Collateral	200,000		2,100,000
Liability Derivatives	5,300,000		4,500,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0		0
Derivative Liability	5,300,000		4,500,000
Derivative, Collateral, Right to Reclaim Securities	(1,700,000)		(1,500,000)
Derivative, Collateral, Right to Reclaim Cash	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	3,600,000		3,000,000
Foreign exchange options
Fair Value of Derivative Instruments
Asset Derivatives	100,000		200,000
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0		0
Derivative Asset	100,000		200,000
Derivative, Collateral, Obligation to Return Securities	(100,000)		(200,000)
Derivative, Collateral, Obligation to Return Cash	0		0
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		0
Level 2
Debt
Aggregate fair value of all debt			16,547,300,000		15,529,400,000
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	0
Realized gains (losses) included in earnings	0
Unrealized holding gains (losses) on securities, (net of tax of 2013: $0; 2012: $0; and 2011: $0.1)	21,000,000		0
Purchases	130,000,000
Settlements	0
Balance at the end of period	151,000,000		0
Fair Value, Measurements, Nonrecurring
Long Lived Assets
Fair Value, Measurement with Unobservable Inputs Reconciliation, Nonrecurring Basis, Asset Value	279,000,000
Recurring | Derivatives not designated as hedging instruments
Fair Value of Derivative Instruments
Liability Derivatives			5,500,000
Amount of Gain or (Loss) Recognized in Income on Derivatives	(21,100,000)		(15,500,000)
Recurring | Derivatives not designated as hedging instruments | Gasoline swaps
Fair Value of Derivative Instruments
Amount of Gain or (Loss) Recognized in Income on Derivatives	2,200,000		700,000
Recurring | Derivatives not designated as hedging instruments | Interest rate caps
Fair Value of Derivative Instruments
Amount of Gain or (Loss) Recognized in Income on Derivatives	(500,000)		(800,000)
Recurring | Derivatives not designated as hedging instruments | Foreign exchange forward contracts
Fair Value of Derivative Instruments
Amount of Gain or (Loss) Recognized in Income on Derivatives	(22,600,000)		(15,400,000)
Recurring | Derivatives not designated as hedging instruments | Foreign exchange options
Fair Value of Derivative Instruments
Amount of Gain or (Loss) Recognized in Income on Derivatives	(200,000)		0
Recurring | Level 1 | Derivatives not designated as hedging instruments
Fair Value of Derivative Instruments
Asset Derivatives	0		0
Liability Derivatives	0		0
Recurring | Level 1 | Derivatives not designated as hedging instruments | Gasoline swaps
Fair Value of Derivative Instruments
Asset Derivatives	0
Liability Derivatives			0
Recurring | Level 1 | Derivatives not designated as hedging instruments | Interest rate caps
Fair Value of Derivative Instruments
Asset Derivatives	0		0
Liability Derivatives	0		0
Recurring | Level 1 | Derivatives not designated as hedging instruments | Foreign exchange forward contracts
Fair Value of Derivative Instruments
Asset Derivatives	0		0
Liability Derivatives	0		0
Recurring | Level 1 | Derivatives not designated as hedging instruments | Foreign exchange options
Fair Value of Derivative Instruments
Asset Derivatives	0		0
Recurring | Level 2
Debt
Aggregate carrying value of all debt			16,218,000,000		14,999,100,000
Recurring | Level 2 | Derivatives not designated as hedging instruments
Fair Value of Derivative Instruments
Asset Derivatives	12,700,000	[1],[2]	4,500,000	[1],[2]
Liability Derivatives	14,200,000	[1],[2]	5,500,000	[1],[2]
Recurring | Level 2 | Derivatives not designated as hedging instruments | Gasoline swaps
Fair Value of Derivative Instruments
Asset Derivatives	1,800,000	[1],[2]	0	[1],[2]
Liability Derivatives	0	[1],[2]	100,000	[1],[2]
Recurring | Level 2 | Derivatives not designated as hedging instruments | Interest rate caps
Fair Value of Derivative Instruments
Asset Derivatives	9,100,000	[1],[2]	900,000	[1],[2]
Liability Derivatives	8,900,000	[1],[2]	900,000	[1],[2]
Recurring | Level 2 | Derivatives not designated as hedging instruments | Foreign exchange forward contracts
Fair Value of Derivative Instruments
Asset Derivatives	1,700,000	[1],[2]	3,400,000	[1],[2]
Liability Derivatives	5,300,000	[1],[2]	4,500,000	[1],[2]
Recurring | Level 2 | Derivatives not designated as hedging instruments | Foreign exchange options
Fair Value of Derivative Instruments
Asset Derivatives	100,000	[1],[2]	200,000	[1],[2]
Liability Derivatives	0	[1],[2]	0	[1],[2]
Recurring | Level 3 | Derivatives not designated as hedging instruments
Fair Value of Derivative Instruments
Asset Derivatives	0		0
Liability Derivatives	0		0
Recurring | Level 3 | Derivatives not designated as hedging instruments | Gasoline swaps
Fair Value of Derivative Instruments
Asset Derivatives	0
Liability Derivatives			0
Recurring | Level 3 | Derivatives not designated as hedging instruments | Interest rate caps
Fair Value of Derivative Instruments
Asset Derivatives	0		0
Liability Derivatives	0		0
Recurring | Level 3 | Derivatives not designated as hedging instruments | Foreign exchange forward contracts
Fair Value of Derivative Instruments
Asset Derivatives	0		0
Liability Derivatives	0		0
Recurring | Level 3 | Derivatives not designated as hedging instruments | Foreign exchange options
Fair Value of Derivative Instruments
Asset Derivatives	0		0
Recurring | Total | Derivatives not designated as hedging instruments
Fair Value of Derivative Instruments
Asset Derivatives	12,700,000		4,500,000
Liability Derivatives	14,200,000
Recurring | Total | Derivatives not designated as hedging instruments | Gasoline swaps
Fair Value of Derivative Instruments
Asset Derivatives	1,800,000
Liability Derivatives			100,000
Recurring | Total | Derivatives not designated as hedging instruments | Interest rate caps
Fair Value of Derivative Instruments
Asset Derivatives	9,100,000		900,000
Liability Derivatives	8,900,000		900,000
Recurring | Total | Derivatives not designated as hedging instruments | Foreign exchange forward contracts
Fair Value of Derivative Instruments
Asset Derivatives	1,700,000		3,400,000
Liability Derivatives	5,300,000		4,500,000
Recurring | Total | Derivatives not designated as hedging instruments | Foreign exchange options
Fair Value of Derivative Instruments
Asset Derivatives	$ 100,000		$ 200,000
Maximum | Fair Value, Measurements, Nonrecurring
Long Lived Assets
Fair Value Inputs, Probability of Payment	0.00%
Fair Value Inputs, Probability of Buy-Out	60.00%
Fair Value Inputs, Probability of Bankruptcy	100.00%
Minimum | Fair Value, Measurements, Nonrecurring
Long Lived Assets
Fair Value Inputs, Probability of Buy-Out	0.00%
Fair Value Inputs, Probability of Bankruptcy	0.00%

[1] All asset derivatives are recorded in "Prepaid expenses and other assets" and all liability derivatives are recorded in "Accrued liabilities" on our consolidated balance sheets.

[2] All fair value measurements were primarily based upon significant observable (Level 2) inputs.