Business Segments (Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Business Segments [Line items]
Revenue	$ 1,085,369	$ 1,066,465
Income from construction operations	40,122	20,084
Other income (expense), net	682	(754)
Interest expense	(14,080)	(11,125)
INCOME BEFORE INCOME TAXES	26,724	8,205
Elimination Of Intersegment Revenues [Member]
Business Segments [Line items]
Revenue	(51,899)	(35,491)
Operating segment [Member]
Business Segments [Line items]
Revenue	1,137,268	1,101,956
Reportable Segments [Member]
Business Segments [Line items]
Revenue	1,085,369	1,066,465
Income from construction operations	55,528	38,838
Reportable Segments [Member] | Elimination Of Intersegment Revenues [Member]
Business Segments [Line items]
Revenue	(51,899)	(35,491)
Reportable Segments [Member] | Operating segment [Member]
Business Segments [Line items]
Revenue	1,137,268	1,101,956
Civil [Member]
Business Segments [Line items]
Revenue	335,858	374,674
Income from construction operations	33,665	30,593
Civil [Member] | Elimination Of Intersegment Revenues [Member]
Business Segments [Line items]
Revenue	(31,643)	(18,202)
Civil [Member] | Operating segment [Member]
Business Segments [Line items]
Revenue	367,501	392,876
Building [Member]
Business Segments [Line items]
Revenue	467,738	398,830
Income from construction operations	12,450	(2,279)
Building [Member] | Elimination Of Intersegment Revenues [Member]
Business Segments [Line items]
Revenue	(20,256)	(17,233)
Building [Member] | Operating segment [Member]
Business Segments [Line items]
Revenue	487,994	416,063
Specialty Contractors [Member]
Business Segments [Line items]
Revenue	281,773	292,961
Income from construction operations	9,413	10,524
Specialty Contractors [Member] | Elimination Of Intersegment Revenues [Member]
Business Segments [Line items]
Revenue		(56)
Specialty Contractors [Member] | Operating segment [Member]
Business Segments [Line items]
Revenue	281,773	293,017
Corporate [Member]
Business Segments [Line items]
Income from construction operations	$ (15,406)	$ (18,754)