Revenue (Schedule Of Revenue By Contract Type) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 1,219,243	$ 1,276,427	$ 2,426,838	$ 2,527,156
Fixed price
Disaggregation of Revenue [Line Items]
Revenue	802,707	775,688	1,599,780	1,538,773
Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	250,463	253,057	523,317	493,687
Unit price
Disaggregation of Revenue [Line Items]
Revenue	115,655	130,861	196,796	223,904
Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	50,418	116,821	106,945	270,792
Civil
Disaggregation of Revenue [Line Items]
Revenue	555,352	568,976	1,030,927	1,055,605
Civil | Fixed price
Disaggregation of Revenue [Line Items]
Revenue	461,068	455,928	880,224	864,899
Civil | Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	498	281	1,768	589
Civil | Unit price
Disaggregation of Revenue [Line Items]
Revenue	88,516	111,790	141,249	183,148
Civil | Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	5,270	977	7,686	6,969
Building
Disaggregation of Revenue [Line Items]
Revenue	382,660	473,021	789,893	954,785
Building | Fixed price
Disaggregation of Revenue [Line Items]
Revenue	95,349	114,229	179,798	219,827
Building | Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	247,402	248,738	517,856	486,511
Building | Unit price
Disaggregation of Revenue [Line Items]
Revenue	(1,564)	629	(1,453)	1,163
Building | Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	41,473	109,425	93,692	247,284
Specialty Contractors
Disaggregation of Revenue [Line Items]
Revenue	281,231	234,430	606,018	516,766
Specialty Contractors | Fixed price
Disaggregation of Revenue [Line Items]
Revenue	246,290	205,531	539,758	454,047
Specialty Contractors | Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	2,563	4,038	3,693	6,587
Specialty Contractors | Unit price
Disaggregation of Revenue [Line Items]
Revenue	28,703	18,442	57,000	39,593
Specialty Contractors | Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	$ 3,675	$ 6,419	$ 5,567	$ 16,539