Business Combinations (Details 1) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010
Summary of unaudited consolidated pro forma results of operations
Revenues	$ 11,755,235	$ 10,848,317
Income from continuing operations	178,954	130,227
Net income	$ 180,757	$ 114,958
Income from continuing operations per diluted common share	$ 1.96	$ 1.41
Net income per diluted common share	$ 1.98	$ 1.25

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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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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