Revenue (Schedule Of Revenue By Contract Type) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Contracts Revenue	$ 1,120,085	$ 1,247,274	$ 2,148,241	$ 2,364,635
Fixed Price [Member]
Contracts Revenue	591,079		1,101,407
Guaranteed Maximum Price [Member]
Contracts Revenue	291,005		573,685
Unit Price [Member]
Contracts Revenue	139,451		223,679
Cost Plus Fee And Other [Member]
Contracts Revenue	98,550		249,470
Civil [Member]
Contracts Revenue	402,473	472,582	665,587	777,157
Civil [Member] | Fixed Price [Member]
Contracts Revenue	259,927		443,830
Civil [Member] | Guaranteed Maximum Price [Member]
Contracts Revenue	3,103		8,175
Civil [Member] | Unit Price [Member]
Contracts Revenue	121,447		190,201
Civil [Member] | Cost Plus Fee And Other [Member]
Contracts Revenue	17,996		23,381
Building [Member]
Contracts Revenue	446,979	492,835	937,220	989,925
Building [Member] | Fixed Price [Member]
Contracts Revenue	96,657		175,658
Building [Member] | Guaranteed Maximum Price [Member]
Contracts Revenue	270,440		532,468
Building [Member] | Unit Price [Member]
Contracts Revenue	10,771		19,588
Building [Member] | Cost Plus Fee And Other [Member]
Contracts Revenue	69,111		209,506
Specialty Contractors [Member]
Contracts Revenue	270,633	$ 281,857	545,434	$ 597,553
Specialty Contractors [Member] | Fixed Price [Member]
Contracts Revenue	234,495		481,919
Specialty Contractors [Member] | Guaranteed Maximum Price [Member]
Contracts Revenue	17,462		33,042
Specialty Contractors [Member] | Unit Price [Member]
Contracts Revenue	7,233		13,890
Specialty Contractors [Member] | Cost Plus Fee And Other [Member]
Contracts Revenue	$ 11,443		$ 16,583