Reportable Operating Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended												6 Months Ended	12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2014 segment	Dec. 31, 2014 segment	Dec. 31, 2013	Dec. 31, 2012
Reportable Operating Segments
Number of operating segments													3	3
Segment reporting information
Revenue	$ 487,592	$ 613,237	$ 515,291	$ 470,074	$ 537,879	$ 551,333	$ 445,013	$ 409,995	$ 480,883	$ 431,842	$ 337,436	$ 291,573		$ 2,086,194	$ 1,944,220	$ 1,541,734
% of Revenue														100.00%	100.00%	100.00%
Gross Profit	49,616	75,473	61,194	49,757	74,917	75,465	59,537	46,096	54,819	56,291	44,004	37,596		236,040	256,015	192,710
% of Segment Revenue														11.30%	13.20%	12.50%
Goodwill	119,410				118,626									119,410	118,626
West
Segment reporting information
Revenue														964,093	1,151,433	832,860
% of Revenue														46.20%	59.20%	54.00%
Gross Profit														143,468	190,747	119,328
% of Segment Revenue														14.90%	16.60%	14.30%
Goodwill	45,239				45,239									45,239	45,239
East
Segment reporting information
Revenue														489,926	430,438	469,963
% of Revenue														23.50%	22.10%	30.50%
Gross Profit														25,749	24,309	40,185
% of Segment Revenue														5.30%	5.60%	8.60%
Goodwill	43,267				43,267									43,267	43,267
Energy
Segment reporting information
Revenue														632,175	362,349	238,911
% of Revenue														30.30%	18.70%	15.50%
Gross Profit														66,823	40,959	33,197
% of Segment Revenue														10.60%	11.30%	13.90%
Goodwill	$ 30,904				$ 30,120									$ 30,904	$ 30,120