Mergers and Acquisitions (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2011
Acquisitions That Are Material in the Aggregate [Member]
Pro Forma (unaudited) financial Information [Abstract]
Revenues	$ 1,167,866	$ 2,780,107
Income from Construction Operations	63,166	126,737
Net Income	36,330	63,395
Basic earnings per common share (in dollars per share)	$ 0.77	$ 1.34
Diluted earnings per common share (in dollars per share)	$ 0.76	$ 1.32
GreenStar Services Corporation [Member]
Pro Forma (unaudited) financial Information [Abstract]
Revenues	1,166,410	2,954,044
Income from Construction Operations	62,372	155,667
Net Income	35,740	83,909
Basic earnings per common share (in dollars per share)	$ 0.76	$ 1.78
Diluted earnings per common share (in dollars per share)	$ 0.75	$ 1.75
Lunda Construction Company [Member]
Pro Forma (unaudited) financial Information [Abstract]
Revenues	1,166,410	2,757,934
Income from Construction Operations	62,136	139,481
Net Income	$ 35,539	$ 73,603
Basic earnings per common share (in dollars per share)	$ 0.75	$ 1.56
Diluted earnings per common share (in dollars per share)	$ 0.74	$ 1.54

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 54

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 55

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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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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