Business Segments (Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reportable segment information
Revenues	$ 1,340,739	$ 1,250,689	$ 3,719,642	$ 3,290,432
Income from construction operations:
Income from construction operations	38,974	70,354	89,939	177,294
Elimination Of Intersegment Revenues [Member]
Reportable segment information
Revenues	(95,202)	(21,789)	(190,660)	(72,333)
Operating segment [Member]
Reportable segment information
Revenues	1,435,941	1,272,478	3,910,302	3,362,765
Reportable Segments [Member]
Reportable segment information
Revenues	1,340,739	1,250,689	3,719,642	3,290,432
Income from construction operations:
Income from construction operations	54,687	83,719	141,007	216,013
Reportable Segments [Member] | Elimination Of Intersegment Revenues [Member]
Reportable segment information
Revenues	(95,202)	(21,789)	(190,660)	(72,333)
Reportable Segments [Member] | Operating segment [Member]
Reportable segment information
Revenues	1,435,941	1,272,478	3,910,302	3,362,765
Civil [Member]
Reportable segment information
Revenues	540,250	482,670	1,449,104	1,238,365
Income from construction operations:
Income from construction operations	43,183	53,684	120,106	156,031
Civil [Member] | Elimination Of Intersegment Revenues [Member]
Reportable segment information
Revenues	(64,067)	(13,472)	(121,449)	(32,292)
Civil [Member] | Operating segment [Member]
Reportable segment information
Revenues	604,317	496,142	1,570,553	1,270,657
Building [Member]
Reportable segment information
Revenues	475,124	412,087	1,325,357	1,082,031
Income from construction operations:
Income from construction operations	6,763	19,159	(8,107)	28,656
Building [Member] | Elimination Of Intersegment Revenues [Member]
Reportable segment information
Revenues	(31,135)	(8,317)	(69,211)	(40,041)
Building [Member] | Operating segment [Member]
Reportable segment information
Revenues	506,259	420,404	1,394,568	1,122,072
Specialty Contractors [Member]
Reportable segment information
Revenues	325,365	355,932	945,181	970,036
Income from construction operations:
Income from construction operations	4,741	10,876	29,008	31,326
Specialty Contractors [Member] | Operating segment [Member]
Reportable segment information
Revenues	325,365	355,932	945,181	970,036
Corporate [Member]
Income from construction operations:
Income from construction operations	$ (15,713)	$ (13,365)	$ (51,068)	$ (38,719)