Business Combinations (Details 3) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Summary of unaudited consolidated pro forma results of operations
Revenues	$ 3,892,754	$ 3,547,785	$ 11,244,562	$ 10,419,047
Income from continuing operations	68,843	50,454	200,498	162,012
Net income	$ 67,844	$ 49,638	$ 197,544	$ 156,388
Income from continuing operations per diluted common share (in dollars per share)	$ 0.76	$ 0.56	$ 2.21	$ 1.78
Net income per diluted common share (in dollars per share)	$ 0.75	$ 0.55	$ 2.19	$ 1.73

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(2)-(3)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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The pro forma income from continuing operations before changes in accounting and extraordinary items, net of tax effect, per diluted share of common stock 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 income from continuing operations before changes in accounting and extraordinary items, net of tax effect, 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 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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