Business Segments (Reportable Segments) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reportable segment information
Revenues		$ 1,312,438	$ 1,084,510	$ 2,378,903	$ 2,039,743
Income from construction operations:
Income from construction operations		30,881	65,443	50,965	106,940
Elimination Of Intersegment Revenues [Member]
Reportable segment information
Revenues		(59,967)	(25,925)	(95,458)	(50,544)
Operating segment [Member]
Reportable segment information
Revenues		1,372,405	1,110,435	2,474,361	2,090,287
Reportable Segments [Member]
Reportable segment information
Revenues		1,312,438	1,084,510	2,378,903	2,039,743
Income from construction operations:
Income from construction operations		47,480	78,309	86,320	132,294
Reportable Segments [Member] | Elimination Of Intersegment Revenues [Member]
Reportable segment information
Revenues		(59,967)	(25,925)	(95,458)	(50,544)
Reportable Segments [Member] | Operating segment [Member]
Reportable segment information
Revenues		1,372,405	1,110,435	2,474,361	2,090,287
Civil [Member]
Reportable segment information
Revenues		534,180	390,539	908,854	755,695
Income from construction operations:
Income from construction operations		46,329	58,002	76,923	102,347
Civil [Member] | Elimination Of Intersegment Revenues [Member]
Reportable segment information
Revenues		(39,180)	(7,584)	(57,382)	(18,820)
Civil [Member] | Operating segment [Member]
Reportable segment information
Revenues		573,360	398,123	966,236	774,515
Building [Member]
Reportable segment information
Revenues		451,404	372,012	850,233	669,944
Income from construction operations:
Income from construction operations		(12,592)	7,674	(14,870)	9,497
Building [Member] | Elimination Of Intersegment Revenues [Member]
Reportable segment information
Revenues		(20,843)	(18,341)	(38,076)	(31,724)
Building [Member] | Operating segment [Member]
Reportable segment information
Revenues		472,247	390,353	888,309	701,668
Specialty Contractors [Member]
Reportable segment information
Revenues		326,854	321,959	619,816	614,104
Income from construction operations:
Income from construction operations		13,743	12,633	24,267	20,450
Specialty Contractors [Member] | Elimination Of Intersegment Revenues [Member]
Reportable segment information
Revenues		56
Specialty Contractors [Member] | Operating segment [Member]
Reportable segment information
Revenues		326,798	321,959	619,816	614,104
Corporate [Member]
Income from construction operations:
Income from construction operations	[1]	$ (16,599)	$ (12,866)	$ (35,355)	$ (25,354)

[1] Consists primarily of corporate general and administrative expenses.