Revenue (Disaggregation Of Revenue) (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
State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	688,272	808,394	1,995,967	2,258,527
Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	113,833	110,615	341,390	277,535
Private owners
Disaggregation of Revenue [Line Items]
Revenue	376,117	523,082	1,267,703	1,433,185
Civil
Disaggregation of Revenue [Line Items]
Revenue	546,218	611,996	1,577,145	1,667,601
Civil | State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	478,720	526,771	1,350,555	1,426,644
Civil | Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	48,680	48,861	149,648	128,112
Civil | Private owners
Disaggregation of Revenue [Line Items]
Revenue	18,818	36,364	76,942	112,845
Civil | Mass transit (includes certain transportation and tunneling projects)
Disaggregation of Revenue [Line Items]
Revenue	386,913	372,131	1,062,322	1,024,083
Civil | Bridges
Disaggregation of Revenue [Line Items]
Revenue	67,117	104,722	179,059	246,006
Civil | Military defense facilities
Disaggregation of Revenue [Line Items]
Revenue	46,615	44,246	140,736	102,898
Civil | Water
Disaggregation of Revenue [Line Items]
Revenue	22,470	23,277	74,080	76,569
Civil | Highways
Disaggregation of Revenue [Line Items]
Revenue	7,101	30,086	48,153	98,259
Civil | Other
Disaggregation of Revenue [Line Items]
Revenue	16,002	37,534	72,795	119,786
Building
Disaggregation of Revenue [Line Items]
Revenue	360,941	508,140	1,150,834	1,462,925
Building | State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	99,540	126,448	268,396	430,212
Building | Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	50,437	32,392	150,085	99,013
Building | Private owners
Disaggregation of Revenue [Line Items]
Revenue	210,964	349,300	732,353	933,700
Building | Mass transit (includes certain transportation and tunneling projects)
Disaggregation of Revenue [Line Items]
Revenue	38,868	50,206	99,747	174,605
Building | Other
Disaggregation of Revenue [Line Items]
Revenue	21,068	32,708	76,507	100,525
Building | Commercial and industrial facilities
Disaggregation of Revenue [Line Items]
Revenue	75,402	162,364	307,414	402,312
Building | Hospitality and gaming
Disaggregation of Revenue [Line Items]
Revenue	89,317	119,588	276,029	346,517
Building | Municipal and government
Disaggregation of Revenue [Line Items]
Revenue	76,471	66,505	222,855	215,230
Building | Education facilities
Disaggregation of Revenue [Line Items]
Revenue	39,528	50,425	123,988	129,085
Building | Health care facilities
Disaggregation of Revenue [Line Items]
Revenue	20,287	26,344	44,294	94,651
Specialty Contractors
Disaggregation of Revenue [Line Items]
Revenue	271,063	321,955	877,081	838,721
Specialty Contractors | State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	110,012	155,175	377,016	401,671
Specialty Contractors | Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	14,716	29,362	41,657	50,410
Specialty Contractors | Private owners
Disaggregation of Revenue [Line Items]
Revenue	146,335	137,418	458,408	386,640
Specialty Contractors | Mass transit (includes certain transportation and tunneling projects)
Disaggregation of Revenue [Line Items]
Revenue	135,971	179,875	465,179	447,180
Specialty Contractors | Water
Disaggregation of Revenue [Line Items]
Revenue	29,161	20,413	67,829	46,341
Specialty Contractors | Other
Disaggregation of Revenue [Line Items]
Revenue	30,104	29,039	87,635	87,569
Specialty Contractors | Commercial and industrial facilities
Disaggregation of Revenue [Line Items]
Revenue	33,897	41,378	109,283	115,382
Specialty Contractors | Education facilities
Disaggregation of Revenue [Line Items]
Revenue	13,876	12,236	45,657	39,131
Specialty Contractors | Multi-unit residential
Disaggregation of Revenue [Line Items]
Revenue	$ 28,054	$ 39,014	$ 101,498	$ 103,118