Acquisitions (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
Schedule of unaudited proforma information
Revenue - As reported	$ 1,570,720	$ 1,316,948	$ 4,509,440	$ 3,823,009
Net earnings - As reported	56,524	38,835	121,682	81,049
Net earnings per common share:
Basic - As reported	$ 1.10	$ 0.74	$ 2.37	$ 1.54
Diluted - As reported	$ 1.10	$ 0.74	$ 2.35	$ 1.53
Hill Hire and TLC [Member]
Schedule of unaudited proforma information
Revenue - Pro forma	1,570,720	1,438,920	4,577,010	4,122,729
Net earnings - Pro forma	$ 56,524	$ 44,290	$ 135,337	$ 95,601
Net earnings per common share:
Basic - Pro forma	$ 1.10	$ 0.85	$ 2.64	$ 1.81
Diluted - Pro forma	$ 1.10	$ 0.85	$ 2.62	$ 1.81

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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