Revenue (Disaggregation Of Revenue) (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
State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	697,688	775,199	1,307,695	1,450,133
Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	104,326	88,530	227,557	166,920
Private owners
Disaggregation of Revenue [Line Items]
Revenue	417,229	412,698	891,586	910,103
Civil
Disaggregation of Revenue [Line Items]
Revenue	555,352	568,976	1,030,927	1,055,605
Civil | State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	481,333	503,828	871,835	899,873
Civil | Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	49,335	42,590	100,968	79,251
Civil | Private owners
Disaggregation of Revenue [Line Items]
Revenue	24,684	22,558	58,124	76,481
Civil | Mass Transit
Disaggregation of Revenue [Line Items]
Revenue	366,534	354,809	675,409	651,952
Civil | Bridges
Disaggregation of Revenue [Line Items]
Revenue	65,775	89,100	111,942	141,284
Civil | Military Defense Facilities
Disaggregation of Revenue [Line Items]
Revenue	44,585	35,042	94,121	58,652
Civil | Water
Disaggregation of Revenue [Line Items]
Revenue	24,800	29,548	51,610	53,292
Civil | Highways
Disaggregation of Revenue [Line Items]
Revenue	29,726	35,591	41,052	68,173
Civil | Other
Disaggregation of Revenue [Line Items]
Revenue	23,932	24,886	56,793	82,252
Building
Disaggregation of Revenue [Line Items]
Revenue	382,660	473,021	789,893	954,785
Building | State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	92,275	157,748	168,856	303,764
Building | Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	49,287	34,648	99,648	66,621
Building | Private owners
Disaggregation of Revenue [Line Items]
Revenue	241,098	280,625	521,389	584,400
Building | Mass Transit
Disaggregation of Revenue [Line Items]
Revenue	34,344	66,552	60,879	124,399
Building | Other
Disaggregation of Revenue [Line Items]
Revenue	9,868	19,848	19,763	44,744
Building | Commercial And Industrial Facilities
Disaggregation of Revenue [Line Items]
Revenue	101,960	106,899	232,012	239,948
Building | Hospitality And Gaming
Disaggregation of Revenue [Line Items]
Revenue	86,145	107,942	186,712	226,929
Building | Municipal And Government
Disaggregation of Revenue [Line Items]
Revenue	74,475	79,223	146,384	148,725
Building | Education Facilities
Disaggregation of Revenue [Line Items]
Revenue	46,143	47,038	84,460	78,660
Building | Mixed Use
Disaggregation of Revenue [Line Items]
Revenue	16,127	13,101	35,676	23,073
Building | Health Care Facilities
Disaggregation of Revenue [Line Items]
Revenue	13,598	32,418	24,007	68,307
Specialty Contractors
Disaggregation of Revenue [Line Items]
Revenue	281,231	234,430	606,018	516,766
Specialty Contractors | State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	124,080	113,623	267,004	246,496
Specialty Contractors | Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	5,704	11,292	26,941	21,048
Specialty Contractors | Private owners
Disaggregation of Revenue [Line Items]
Revenue	151,447	109,515	312,073	249,222
Specialty Contractors | Mass Transit
Disaggregation of Revenue [Line Items]
Revenue	148,045	118,634	329,208	267,305
Specialty Contractors | Water
Disaggregation of Revenue [Line Items]
Revenue	17,514	16,090	38,668	25,928
Specialty Contractors | Other
Disaggregation of Revenue [Line Items]
Revenue	16,021	20,722	34,052	34,192
Specialty Contractors | Commercial And Industrial Facilities
Disaggregation of Revenue [Line Items]
Revenue	36,637	20,499	75,386	74,004
Specialty Contractors | Education Facilities
Disaggregation of Revenue [Line Items]
Revenue	18,425	10,338	31,781	26,895
Specialty Contractors | Mixed Use
Disaggregation of Revenue [Line Items]
Revenue	13,940	10,536	23,479	24,338
Specialty Contractors | Multi Unit Residential
Disaggregation of Revenue [Line Items]
Revenue	$ 30,649	$ 37,611	$ 73,444	$ 64,104