Reportable Operating Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 item	Jun. 30, 2012	Dec. 31, 2012
Reportable Operating Segments
Number of operating segments			3
Segment reporting information
Revenue	$ 445,013	$ 337,436	$ 855,008	$ 629,009
% of Segment Revenue	100.00%	100.00%	100.00%	100.00%
Gross Profit	59,537	44,004	105,633	81,600
% of Segment Revenue	13.40%	13.00%	12.40%	13.00%
Goodwill	118,028		118,028		116,941
East Construction Services
Segment reporting information
Revenue	175,398	156,057	365,609	277,907
% of Segment Revenue	39.40%	46.20%	42.80%	44.20%
Gross Profit	15,215	17,360	30,210	28,778
% of Segment Revenue	8.70%	11.10%	8.30%	10.40%
Goodwill	70,946		70,946		69,859
West Construction Services
Segment reporting information
Revenue	258,194	167,287	465,880	325,318
% of Segment Revenue	58.00%	49.60%	54.40%	51.70%
Gross Profit	41,956	24,294	70,675	48,695
% of Segment Revenue	16.20%	14.50%	15.20%	15.00%
Goodwill	44,641		44,641		44,641
Engineering
Segment reporting information
Revenue	11,421	14,092	23,519	25,784
% of Segment Revenue	2.60%	4.20%	2.80%	4.10%
Gross Profit	2,396	2,350	4,748	4,127
% of Segment Revenue	21.00%	16.70%	20.20%	16.00%
Goodwill	$ 2,441		$ 2,441		$ 2,441

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph l

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 20

-Section 50

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

-Publisher FASB

-Name Accounting Standards Codification

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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.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

-Paragraph 43

-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 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 72

-Subparagraph d

-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 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

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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.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 34

-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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