Goodwill and Other Intangible Assets (Schedule of Goodwill by Segment) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Goodwill [Line Items]
Goodwill, gross	$ 1,458,700
Accumulated impairment loss	(127,000)
Goodwill, net	1,331,699	$ 1,243,034
Communications
Goodwill [Line Items]
Goodwill, gross	584,700
Accumulated impairment loss	0
Goodwill, net	584,700
Clean Energy and Infrastructure
Goodwill [Line Items]
Goodwill, gross	164,400
Accumulated impairment loss	0
Goodwill, net	164,400
Oil and Gas
Goodwill [Line Items]
Goodwill, gross	513,200
Accumulated impairment loss	(127,000)
Goodwill, net	386,200
Electrical Transmission
Goodwill [Line Items]
Goodwill, gross	196,400
Accumulated impairment loss	0
Goodwill, net	$ 196,400