Revenue from Contracts with Customers - Schedule of Disaggregation of Revenues (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues		$ 9,903,580	$ 8,797,061	$ 9,174,611
UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		9,393,629	8,366,498	8,751,352
United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		2,015,466	1,806,092	1,961,798
United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		3,922,864	3,485,495	3,340,337
United States Building Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		2,468,892	2,134,016	2,121,661
United States Industrial Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		986,407	940,895	1,327,556
United Kingdom Building Services | UNITED KINGDOM
Disaggregation of Revenue [Line Items]
Revenues		509,951	430,563	423,259
Operating Segments [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		2,018,706	1,811,217	1,965,026
Operating Segments [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		3,930,753	3,492,013	3,351,918
Intersegment Eliminations [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		(3,240)	(5,125)	(3,228)
Intersegment Eliminations [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		(7,889)	(6,518)	(11,581)
Commercial Market Sector [Member] | Operating Segments [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 1,059,908	$ 963,452	$ 1,078,200
Percent of individual segment		52.00%	53.00%	55.00%
Commercial Market Sector [Member] | Operating Segments [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 1,525,816	$ 1,316,013	$ 1,185,129
Percent of individual segment		39.00%	38.00%	36.00%
Manufacturing Market Sector [Member] | Operating Segments [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 226,644	$ 241,415	$ 224,913
Percent of individual segment		11.00%	13.00%	11.00%
Manufacturing Market Sector [Member] | Operating Segments [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 523,896	$ 430,365	$ 533,699
Percent of individual segment		13.00%	12.00%	16.00%
Healthcare Market Sector [Member] | Operating Segments [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 106,412	$ 72,778	$ 85,088
Percent of individual segment		5.00%	4.00%	4.00%
Healthcare Market Sector [Member] | Operating Segments [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 489,028	$ 349,235	$ 304,622
Percent of individual segment		12.00%	10.00%	9.00%
Institutional Market Sector [Member] | Operating Segments [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 177,312	$ 140,837	$ 120,991
Percent of individual segment		9.00%	8.00%	6.00%
Institutional Market Sector [Member] | Operating Segments [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 280,463	$ 377,780	$ 313,409
Percent of individual segment		7.00%	11.00%	9.00%
Transportation Market Sector [Member] | Operating Segments [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 196,313	$ 192,656	$ 209,830
Percent of individual segment		10.00%	11.00%	11.00%
Transportation Market Sector [Member] | Operating Segments [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 84,503	$ 70,692	$ 32,686
Percent of individual segment		2.00%	2.00%	1.00%
Water and Wastewater Market Sector [Member] | Operating Segments [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 14,962	$ 6,882	$ 19,888
Percent of individual segment		1.00%	1.00%	1.00%
Water and Wastewater Market Sector [Member] | Operating Segments [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 213,315	$ 185,996	$ 202,428
Percent of individual segment		6.00%	5.00%	6.00%
Hospitality Market Sector [Member] | Operating Segments [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 15,342	$ 23,797	$ 16,985
Percent of individual segment		1.00%	1.00%	1.00%
Hospitality Market Sector [Member] | Operating Segments [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 38,405	$ 40,079	$ 35,385
Percent of individual segment		1.00%	1.00%	1.00%
Short Duration Projects [Member] | Operating Segments [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues	[1]	$ 182,614	$ 142,542	$ 170,631
Percent of individual segment		9.00%	8.00%	9.00%
Short Duration Projects [Member] | Operating Segments [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues	[1]	$ 308,467	$ 343,799	$ 365,721
Percent of individual segment		8.00%	10.00%	11.00%
Service Work [Member] | Operating Segments [Member] | United States Electrical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 39,199	$ 26,858	$ 38,500
Percent of individual segment		2.00%	1.00%	2.00%
Service Work [Member] | Operating Segments [Member] | United States Mechanical Construction And Facilities Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 466,860	$ 378,054	$ 378,839
Percent of individual segment		12.00%	11.00%	11.00%
Service Work [Member] | Operating Segments [Member] | United Kingdom Building Services | UNITED KINGDOM
Disaggregation of Revenue [Line Items]
Revenues		$ 261,889	$ 221,373	$ 212,876
Percent of individual segment		51.00%	51.00%	50.00%
Mobile Mechanical Services [Member] | Operating Segments [Member] | United States Building Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 1,501,919	$ 1,282,803	$ 1,253,209
Percent of individual segment		61.00%	60.00%	59.00%
Commercial Site-Based Services [Member] | Operating Segments [Member] | United States Building Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 680,351	$ 587,345	$ 571,345
Percent of individual segment		28.00%	28.00%	27.00%
Government Site-Based Services [Member] | Operating Segments [Member] | United States Building Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 184,272	$ 167,990	$ 176,282
Percent of individual segment		7.00%	8.00%	8.00%
Energy Services [Member] | Operating Segments [Member] | United States Building Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 102,350	$ 95,878	$ 120,825
Percent of individual segment		4.00%	4.00%	6.00%
Field Services [Member] | Operating Segments [Member] | United States Industrial Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 853,143	$ 813,872	$ 1,162,321
Percent of individual segment		86.00%	86.00%	88.00%
Shop Services [Member] | Operating Segments [Member] | United States Industrial Services | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues		$ 133,264	$ 127,023	$ 165,235
Percent of individual segment		14.00%	14.00%	12.00%
Project Work [Member] | Operating Segments [Member] | United Kingdom Building Services | UNITED KINGDOM
Disaggregation of Revenue [Line Items]
Revenues		$ 248,062	$ 209,190	$ 210,383
Percent of individual segment		49.00%	49.00%	50.00%

[1] Represents those projects which generally are completed within three months or less.