Revenue (Schedule Of Revenue By Contract Type) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 1,178,222	$ 1,442,091	$ 3,605,060	$ 3,969,247
Fixed price
Disaggregation of Revenue [Line Items]
Revenue	798,641	887,035	2,398,421	2,494,948
Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	225,317	310,401	748,634	799,428
Unit price
Disaggregation of Revenue [Line Items]
Revenue	95,117	155,951	291,913	379,855
Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	59,147	88,704	166,092	295,016
Civil
Disaggregation of Revenue [Line Items]
Revenue	546,218	611,996	1,577,145	1,667,601
Civil | Fixed price
Disaggregation of Revenue [Line Items]
Revenue	473,212	484,851	1,353,436	1,349,750
Civil | Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	502	179	2,270	768
Civil | Unit price
Disaggregation of Revenue [Line Items]
Revenue	71,429	124,506	212,678	307,654
Civil | Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	1,075	2,460	8,761	9,429
Building
Disaggregation of Revenue [Line Items]
Revenue	360,941	508,140	1,150,834	1,462,925
Building | Fixed price
Disaggregation of Revenue [Line Items]
Revenue	89,895	117,650	269,693	401,957
Building | Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	219,395	308,299	737,251	794,810
Building | Unit price
Disaggregation of Revenue [Line Items]
Revenue	130	254	(1,323)	1,417
Building | Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	51,521	81,937	145,213	264,741
Specialty Contractors
Disaggregation of Revenue [Line Items]
Revenue	271,063	321,955	877,081	838,721
Specialty Contractors | Fixed price
Disaggregation of Revenue [Line Items]
Revenue	235,534	284,534	775,292	743,241
Specialty Contractors | Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	5,420	1,923	9,113	3,850
Specialty Contractors | Unit price
Disaggregation of Revenue [Line Items]
Revenue	23,558	31,191	80,558	70,784
Specialty Contractors | Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	$ 6,551	$ 4,307	$ 12,118	$ 20,846