Business Combinations (Details 1) (USD $) In Thousands, except Per Share data	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Summary of unaudited consolidated pro forma results of operations
Revenues	$ 2,951,046	$ 2,795,667	$ 8,822,713	$ 8,075,752
Income from continuing operations	57,045	36,451	138,110	94,753
Net income	$ 56,045	$ 31,614	$ 132,408	$ 84,441
Income from continuing operations per diluted common share	$ 0.62	$ 0.40	$ 1.50	$ 1.03
Net income per diluted common share	$ 0.61	$ 0.34	$ 1.44	$ 0.92

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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