Revenue (Schedule Of Revenue By Contract Type) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 1,207,595	$ 1,250,729
Fixed price
Disaggregation of Revenue [Line Items]
Revenue	797,073	763,085
Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	272,854	240,630
Unit price
Disaggregation of Revenue [Line Items]
Revenue	81,141	93,043
Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	56,527	153,971
Civil
Disaggregation of Revenue [Line Items]
Revenue	475,575	486,629
Civil | Fixed price
Disaggregation of Revenue [Line Items]
Revenue	419,156	408,971
Civil | Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	1,270	308
Civil | Unit price
Disaggregation of Revenue [Line Items]
Revenue	52,733	71,358
Civil | Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	2,416	5,992
Building
Disaggregation of Revenue [Line Items]
Revenue	407,233	481,764
Building | Fixed price
Disaggregation of Revenue [Line Items]
Revenue	84,449	105,598
Building | Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	270,454	237,773
Building | Unit price
Disaggregation of Revenue [Line Items]
Revenue	111	534
Building | Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	52,219	137,859
Specialty Contractors
Disaggregation of Revenue [Line Items]
Revenue	324,787	282,336
Specialty Contractors | Fixed price
Disaggregation of Revenue [Line Items]
Revenue	293,468	248,516
Specialty Contractors | Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Revenue	1,130	2,549
Specialty Contractors | Unit price
Disaggregation of Revenue [Line Items]
Revenue	28,297	21,151
Specialty Contractors | Cost plus fee and other
Disaggregation of Revenue [Line Items]
Revenue	$ 1,892	$ 10,120