Goodwill and Other Intangible Assets - Schedule of Goodwill by Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Goodwill [Line Items]
Goodwill, gross	$ 1,462,900
Accumulated impairment loss	(124,300)
Goodwill, net	1,338,597	$ 1,243,034
Communications
Goodwill [Line Items]
Goodwill, gross	589,500
Accumulated impairment loss	0
Goodwill, net	589,500
Clean Energy and Infrastructure
Goodwill [Line Items]
Goodwill, gross	165,400
Accumulated impairment loss	0
Goodwill, net	165,400
Oil and Gas
Goodwill [Line Items]
Goodwill, gross	510,100
Accumulated impairment loss	(124,300)
Goodwill, net	385,800
Electrical Transmission
Goodwill [Line Items]
Goodwill, gross	197,900
Accumulated impairment loss	0
Goodwill, net	$ 197,900