Revenue (Disaggregation Of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 1,442,091	$ 1,189,345	$ 3,969,247	$ 3,273,107
State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	808,394	701,136	2,258,527	1,829,491
Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	110,615	74,528	277,535	219,742
Private owners
Disaggregation of Revenue [Line Items]
Revenue	523,082	413,681	1,433,185	1,223,874
Civil
Disaggregation of Revenue [Line Items]
Revenue	611,996	524,546	1,667,601	1,331,698
Civil | State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	526,771	420,839	1,426,644	1,059,384
Civil | Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	48,861	32,852	128,112	82,989
Civil | Private owners
Disaggregation of Revenue [Line Items]
Revenue	36,364	70,855	112,845	189,325
Civil | Mass Transit
Disaggregation of Revenue [Line Items]
Revenue	372,131	265,671	1,024,083	655,541
Civil | Bridges
Disaggregation of Revenue [Line Items]
Revenue	104,722	113,743	246,006	269,517
Civil | Military Defense Facilities
Disaggregation of Revenue [Line Items]
Revenue	44,246	16,914	102,898	40,335
Civil | Highways
Disaggregation of Revenue [Line Items]
Revenue	30,086	44,630	98,259	145,917
Civil | Water
Disaggregation of Revenue [Line Items]
Revenue	23,277	7,555	76,569	21,882
Civil | Other
Disaggregation of Revenue [Line Items]
Revenue	37,534	76,033	119,786	198,506
Building
Disaggregation of Revenue [Line Items]
Revenue	508,140	415,346	1,462,925	1,277,130
Building | State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	126,448	144,106	430,212	422,590
Building | Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	32,392	36,890	99,013	121,437
Building | Private owners
Disaggregation of Revenue [Line Items]
Revenue	349,300	234,350	933,700	733,103
Building | Mass Transit
Disaggregation of Revenue [Line Items]
Revenue	50,206	53,384	174,605	123,772
Building | Commercial And Industrial Facilities
Disaggregation of Revenue [Line Items]
Revenue	162,364	121,206	402,312	345,752
Building | Hospitality And Gaming
Disaggregation of Revenue [Line Items]
Revenue	119,588	57,672	346,517	180,556
Building | Municipal And Government
Disaggregation of Revenue [Line Items]
Revenue	66,505	62,444	215,230	192,986
Building | Education Facilities
Disaggregation of Revenue [Line Items]
Revenue	50,425	33,469	129,085	123,059
Building | Health Care Facilities
Disaggregation of Revenue [Line Items]
Revenue	26,344	58,323	94,651	199,347
Building | Other
Disaggregation of Revenue [Line Items]
Revenue	32,708	28,848	100,525	111,658
Specialty Contractors
Disaggregation of Revenue [Line Items]
Revenue	321,955	249,453	838,721	664,279
Specialty Contractors | State and local agencies
Disaggregation of Revenue [Line Items]
Revenue	155,175	136,191	401,671	347,517
Specialty Contractors | Federal agencies
Disaggregation of Revenue [Line Items]
Revenue	29,362	4,786	50,410	15,316
Specialty Contractors | Private owners
Disaggregation of Revenue [Line Items]
Revenue	137,418	108,476	386,640	301,446
Specialty Contractors | Mass Transit
Disaggregation of Revenue [Line Items]
Revenue	179,875	103,710	447,180	285,121
Specialty Contractors | Water
Disaggregation of Revenue [Line Items]
Revenue	20,413	9,706	46,341	26,143
Specialty Contractors | Commercial And Industrial Facilities
Disaggregation of Revenue [Line Items]
Revenue	41,378	51,471	115,382	139,112
Specialty Contractors | Multi Unit Residential
Disaggregation of Revenue [Line Items]
Revenue	39,014	25,860	103,118	56,474
Specialty Contractors | Education Facilities
Disaggregation of Revenue [Line Items]
Revenue	12,236	21,610	39,131	47,226
Specialty Contractors | Other
Disaggregation of Revenue [Line Items]
Revenue	$ 29,039	$ 37,096	$ 87,569	$ 110,203