Business Segments (Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Business Segments [Line items]
Revenue	$ 1,028,156	$ 1,117,361
INCOME (LOSS) FROM CONSTRUCTION OPERATIONS	(925)	37,017
Capital expenditures	19,970	5,672
Depreciation and amortization	10,187	20,996
External And Intersegment Customers [Member]
Business Segments [Line items]
Revenue	1,090,818	1,169,055
Elimination Of Intersegment Revenues [Member]
Business Segments [Line items]
Revenue	(62,662)	(51,694)
Reportable Segments [Member]
Business Segments [Line items]
Revenue	1,028,156	1,117,361
INCOME (LOSS) FROM CONSTRUCTION OPERATIONS	16,499	51,892
Capital expenditures	19,893	5,618
Depreciation and amortization	7,349	18,028
Reportable Segments [Member] | External And Intersegment Customers [Member]
Business Segments [Line items]
Revenue	1,090,818	1,169,055
Reportable Segments [Member] | Elimination Of Intersegment Revenues [Member]
Business Segments [Line items]
Revenue	(62,662)	(51,694)
Civil [Member]
Business Segments [Line items]
Revenue	263,114	304,575
INCOME (LOSS) FROM CONSTRUCTION OPERATIONS	2,839	31,888
Capital expenditures	19,196	5,567
Depreciation and amortization	5,756	16,318
Civil [Member] | External And Intersegment Customers [Member]
Business Segments [Line items]
Revenue	325,400	338,108
Civil [Member] | Elimination Of Intersegment Revenues [Member]
Business Segments [Line items]
Revenue	(62,286)	(33,533)
Building [Member]
Business Segments [Line items]
Revenue	490,241	497,090
INCOME (LOSS) FROM CONSTRUCTION OPERATIONS	6,425	5,242
Capital expenditures	278	45
Depreciation and amortization	481	518
Building [Member] | External And Intersegment Customers [Member]
Business Segments [Line items]
Revenue	490,617	515,251
Building [Member] | Elimination Of Intersegment Revenues [Member]
Business Segments [Line items]
Revenue	(376)	(18,161)
Specialty Contractors [Member]
Business Segments [Line items]
Revenue	274,801	315,696
INCOME (LOSS) FROM CONSTRUCTION OPERATIONS	7,235	14,762
Capital expenditures	419	6
Depreciation and amortization	1,112	1,192
Specialty Contractors [Member] | External And Intersegment Customers [Member]
Business Segments [Line items]
Revenue	274,801	315,696
Corporate [Member]
Business Segments [Line items]
INCOME (LOSS) FROM CONSTRUCTION OPERATIONS	(17,424)	(14,875)
Capital expenditures	77	54
Depreciation and amortization	$ 2,838	$ 2,968