Goodwill, Identifiable Intangible Assets, And Other Long-Lived Assets - Schedule of Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Goodwill, Beginning balance	$ 851,783,000	$ 1,063,911,000
Acquisitions and purchase price adjustments	38,485,000	13,372,000
Goodwill impairment	0	(225,500,000)	$ 0
Goodwill, intersegment transfers	0
Goodwill, Ending balance	890,268,000	851,783,000	1,063,911,000
United States Electrical Construction And Facilities Services
Goodwill [Roll Forward]
Goodwill, Beginning balance	142,545,000	142,545,000
Acquisitions and purchase price adjustments	24,467,000	0
Goodwill impairment		0
Goodwill, intersegment transfers	(7,500,000)
Goodwill, Ending balance	159,512,000	142,545,000	142,545,000
United States Mechanical Construction And Facilities Services
Goodwill [Roll Forward]
Goodwill, Beginning balance	299,618,000	299,220,000
Acquisitions and purchase price adjustments	4,269,000	398,000
Goodwill impairment		0
Goodwill, intersegment transfers	0
Goodwill, Ending balance	303,887,000	299,618,000	299,220,000
United States Building Services
Goodwill [Roll Forward]
Goodwill, Beginning balance	302,132,000	289,158,000
Acquisitions and purchase price adjustments	9,749,000	12,974,000
Goodwill impairment		0
Goodwill, intersegment transfers	900,000
Goodwill, Ending balance	312,781,000	302,132,000	289,158,000
United States Industrial Services
Goodwill [Roll Forward]
Goodwill, Beginning balance	107,488,000	332,988,000
Acquisitions and purchase price adjustments	0	0
Goodwill impairment		(225,500,000)
Goodwill, intersegment transfers	6,600,000
Goodwill, Ending balance	$ 114,088,000	$ 107,488,000	$ 332,988,000