Business Combinations (Details 3) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Summary of unaudited consolidated pro forma results of operations
Revenues	$ 3,403,722	$ 3,236,892
Income from continuing operations	56,961	50,681
Net income	$ 57,419	$ 47,417
Income from continuing operations per diluted common share (in dollars per share)	$ 0.63	$ 0.56
Net income per diluted common share (in dollars per share)	$ 0.63	$ 0.52

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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