Revenue (Disaggregation Of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
REVENUE	$ 1,349,516	$ 1,442,091	$ 1,276,427	$ 1,250,729	$ 1,177,725	$ 1,189,345	$ 1,125,275	$ 958,487	$ 5,318,763	$ 4,450,832	$ 4,454,662
State and local agencies
Disaggregation of Revenue [Line Items]
REVENUE									2,943,870	2,470,245	2,318,545
Federal agencies
Disaggregation of Revenue [Line Items]
REVENUE									394,327	281,662	350,647
Private owners
Disaggregation of Revenue [Line Items]
REVENUE									1,980,566	1,698,925	1,785,470
Civil
Disaggregation of Revenue [Line Items]
REVENUE									2,199,899	1,779,352	1,586,093
Civil | State and local agencies
Disaggregation of Revenue [Line Items]
REVENUE									1,875,653	1,401,001	1,294,630
Civil | Federal agencies
Disaggregation of Revenue [Line Items]
REVENUE									175,933	116,869	95,567
Civil | Private owners
Disaggregation of Revenue [Line Items]
REVENUE									148,313	261,482	195,896
Civil | Mass transit (includes certain transportation and tunneling projects)
Disaggregation of Revenue [Line Items]
REVENUE									1,367,412	992,755	702,614
Civil | Bridges
Disaggregation of Revenue [Line Items]
REVENUE									306,161	334,117	431,202
Civil | Military defense facilities
Disaggregation of Revenue [Line Items]
REVENUE									146,969	59,082	26,225
Civil | Highways
Disaggregation of Revenue [Line Items]
REVENUE									122,254	86,747	202,423
Civil | Water
Disaggregation of Revenue [Line Items]
REVENUE									101,705	33,370	10,195
Civil | Other
Disaggregation of Revenue [Line Items]
REVENUE									155,398	273,281	213,434
Building
Disaggregation of Revenue [Line Items]
REVENUE									1,984,641	1,742,040	1,861,699
Building | State and local agencies
Disaggregation of Revenue [Line Items]
REVENUE									534,449	573,049	617,133
Building | Federal agencies
Disaggregation of Revenue [Line Items]
REVENUE									143,327	153,467	201,745
Building | Private owners
Disaggregation of Revenue [Line Items]
REVENUE									1,306,865	1,015,524	1,042,821
Building | Mass transit (includes certain transportation and tunneling projects)
Disaggregation of Revenue [Line Items]
REVENUE									218,930	201,400	67,588
Building | Mixed use
Disaggregation of Revenue [Line Items]
REVENUE									59,391	31,685	150,549
Building | Commercial and industrial facilities
Disaggregation of Revenue [Line Items]
REVENUE									580,297	459,806	374,312
Building | Hospitality and gaming
Disaggregation of Revenue [Line Items]
REVENUE									474,329	297,700	301,871
Building | Municipal and government
Disaggregation of Revenue [Line Items]
REVENUE									287,337	254,736	261,496
Building | Education facilities
Disaggregation of Revenue [Line Items]
REVENUE									173,472	143,382	145,147
Building | Health care facilities
Disaggregation of Revenue [Line Items]
REVENUE									117,968	239,299	428,819
Building | Other
Disaggregation of Revenue [Line Items]
REVENUE									72,917	114,032	131,917
Specialty Contractors
Disaggregation of Revenue [Line Items]
REVENUE									1,134,223	929,440	1,006,870
Specialty Contractors | State and local agencies
Disaggregation of Revenue [Line Items]
REVENUE									533,768	496,195	406,782
Specialty Contractors | Federal agencies
Disaggregation of Revenue [Line Items]
REVENUE									75,067	11,326	53,335
Specialty Contractors | Private owners
Disaggregation of Revenue [Line Items]
REVENUE									525,388	421,919	546,753
Specialty Contractors | Mass transit (includes certain transportation and tunneling projects)
Disaggregation of Revenue [Line Items]
REVENUE									592,430	419,402	296,092
Specialty Contractors | Water
Disaggregation of Revenue [Line Items]
REVENUE									73,769	37,403	22,390
Specialty Contractors | Mixed use
Disaggregation of Revenue [Line Items]
REVENUE									47,022	64,302	163,308
Specialty Contractors | Commercial and industrial facilities
Disaggregation of Revenue [Line Items]
REVENUE									152,868	186,819	189,632
Specialty Contractors | Education facilities
Disaggregation of Revenue [Line Items]
REVENUE									44,762	70,229	99,214
Specialty Contractors | Multi-unit residential
Disaggregation of Revenue [Line Items]
REVENUE									139,924	83,903	81,023
Specialty Contractors | Other
Disaggregation of Revenue [Line Items]
REVENUE									$ 83,448	$ 67,382	$ 155,211