Revenue (Schedule Of Revenue By Contract Type) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Contracts Revenue	$ 1,250,729	$ 958,487
Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	763,085	512,490
Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	240,630	212,970
Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	93,043	109,109
Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	153,971	123,918
Civil [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	486,629	333,494
Civil [Member] | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	408,971	242,867
Civil [Member] | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	308	2,233
Civil [Member] | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	71,358	84,878
Civil [Member] | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	5,992	3,516
Building [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	481,764	433,466
Building [Member] | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	105,598	114,359
Building [Member] | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	237,773	207,131
Building [Member] | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	534	5,228
Building [Member] | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	137,859	106,748
Specialty Contractors [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	282,336	191,527
Specialty Contractors [Member] | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	248,516	155,264
Specialty Contractors [Member] | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	2,549	3,606
Specialty Contractors [Member] | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	21,151	19,003
Specialty Contractors [Member] | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	$ 10,120	$ 13,654