Goodwill, Identifiable Intangible Assets, And Other Long-Lived Assets - Narrative (Details) - USD ($)		12 Months Ended
	Oct. 01, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill and Intangible Assets[Line Items]
Goodwill		$ 890,268,000	$ 851,783,000	$ 1,063,911,000
Goodwill acquired		38,300,000	13,100,000
Goodwill impairment		0	225,500,000	0
Goodwill, accumulated impairment loss				268,100,000
Non-cash expense for impairment of intangible and tangible assets, excluding goodwill		0	7,300,000	0
Indefinite-lived intangible asset acquired		$ 70,600,000	38,100,000
Amortization periods		7 years 6 months
Amortization of identifiable intangible assets		$ 64,089,000	59,950,000	48,142,000
Domestic Segments
Goodwill and Intangible Assets[Line Items]
Perpetual growth rate used for annual testing	2.00%
Domestic Construction
Goodwill and Intangible Assets[Line Items]
Weighted average cost of capital used in annual testing for impairment	10.40%
United States Electrical Construction And Facilities Services
Goodwill and Intangible Assets[Line Items]
Goodwill		$ 159,512,000	142,545,000	142,545,000
Goodwill allocated		17.90%
Goodwill impairment			0
Effect of 50 Basis Point Increase in the Weighted Average Costs of Capital		$ 103,600,000
Effect of 50 Basis Point Decrease in the Perpetual Growth Rate		52,400,000
United States Mechanical Construction And Facilities Services
Goodwill and Intangible Assets[Line Items]
Goodwill		$ 303,887,000	299,618,000	299,220,000
Goodwill allocated		34.20%
Goodwill impairment			0
Effect of 50 Basis Point Increase in the Weighted Average Costs of Capital		$ 185,500,000
Effect of 50 Basis Point Decrease in the Perpetual Growth Rate		95,900,000
United States Building Services
Goodwill and Intangible Assets[Line Items]
Goodwill		$ 312,781,000	302,132,000	289,158,000
Goodwill allocated		35.10%
Weighted average cost of capital used in annual testing for impairment	10.40%
Goodwill impairment			0
Effect of 50 Basis Point Increase in the Weighted Average Costs of Capital		$ 74,500,000
Effect of 50 Basis Point Decrease in the Perpetual Growth Rate		35,800,000
Goodwill, accumulated impairment loss				139,500,000
United States Industrial Services
Goodwill and Intangible Assets[Line Items]
Goodwill		$ 114,088,000	107,488,000	332,988,000
Goodwill allocated		12.80%
Weighted average cost of capital used in annual testing for impairment	11.30%
Goodwill impairment			$ 225,500,000
Effect of 50 Basis Point Increase in the Weighted Average Costs of Capital		$ 25,900,000
Effect of 50 Basis Point Decrease in the Perpetual Growth Rate		$ 9,500,000
Goodwill, accumulated impairment loss				$ 128,600,000
Customer relationships
Goodwill and Intangible Assets[Line Items]
Amortization periods		7 years 6 months
Developed technology/Vendor network
Goodwill and Intangible Assets[Line Items]
Amortization periods		5 years 9 months
Trade names (amortized)
Goodwill and Intangible Assets[Line Items]
Amortization periods		8 years 6 months
Contract backlog
Goodwill and Intangible Assets[Line Items]
Amortization periods		3 months