Acquisitions (Details 1) (USD $) In Thousands, except Per Share data	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Schedule of unaudited proforma information
Revenue - As reported	$ 1,513,344	$ 1,286,123	$ 2,938,720	$ 2,506,061
Net earnings - As reported	40,033	29,841	65,158	42,214
Net earnings per common share:
Basic - As reported	$ 0.78	$ 0.57	$ 1.27	$ 0.80
Diluted - As reported	$ 0.77	$ 0.56	$ 1.26	$ 0.79
Hill Hire [Member]
Schedule of unaudited proforma information
Revenue - Pro forma	1,543,084	1,321,924	3,006,290	2,578,223
Net earnings - Pro forma	$ 47,791	$ 28,637	$ 77,773	$ 42,433
Net earnings per common share:
Basic - Pro forma	$ 0.93	$ 0.54	$ 1.51	$ 0.80
Diluted - Pro forma	$ 0.92	$ 0.54	$ 1.50	$ 0.80

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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