Goodwill and Other Intangible Assets (Schedule of Goodwill by Segment) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill, gross	$ 1,343,900
Accumulated impairment loss	(116,500)
Goodwill, net	1,227,405	$ 1,221,440
Communications [Member]
Goodwill [Line Items]
Goodwill, gross	547,500
Accumulated impairment loss	0
Goodwill, net	547,500
Oil and Gas [Member]
Goodwill [Line Items]
Goodwill, gross	493,600
Accumulated impairment loss	(116,500)
Goodwill, net	377,100
Electrical Transmission [Member]
Goodwill [Line Items]
Goodwill, gross	150,100
Accumulated impairment loss	0
Goodwill, net	150,100
Power Generation and Industrial [Member]
Goodwill [Line Items]
Goodwill, gross	152,700
Accumulated impairment loss	0
Goodwill, net	$ 152,700