Acquisitions (Pro Forma Results) (Details) (USD $) In Millions, except Share data	3 Months Ended	9 Months Ended
Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Acquisitions [Abstract]
Revenue	$ 1,026.1	$ 3,223.3	$ 3,042.2
Net income (loss)	$ 60.3	$ (61.5)	$ 119.5
Net income (loss) per share - basic	$ 1.34	$ (1.36)	$ 2.61
Net income (loss) per share - diluted	$ 1.32	$ (1.36)	$ 2.57
Weighted average shares outstanding - basic	44.9	45.4	45.7
Weighted average shares outstanding - diluted	45.7	45.4	46.4

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The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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The weighted average number of shares or units and dilutive common stock or unit equivalents outstanding in the calculation of proforma diluted earnings per share (earnings per unit), which is commonly presented in initial public offerings based on the terms of the offering.

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The weighted average number of shares (units) outstanding in the calculation of pro forma basic earnings per share (earnings per unit), which is commonly presented in initial public offerings based on the terms of the offering.

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