Goodwill and Other Intangible Assets (Schedule of Goodwill by Segment) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill, gross carrying amount	$ 1,064,200
Goodwill, accumulated impairment losses	(72,200)
Goodwill, net	991,975	$ 988,511
Communications [Member]
Goodwill [Line Items]
Goodwill, gross carrying amount	414,900
Goodwill, accumulated impairment losses	0
Goodwill, net	414,900
Oil and Gas [Member]
Goodwill [Line Items]
Goodwill, gross carrying amount	381,800
Goodwill, accumulated impairment losses	(72,200)
Goodwill, net	309,600
Electrical Transmission [Member]
Goodwill [Line Items]
Goodwill, gross carrying amount	149,900
Goodwill, accumulated impairment losses	0
Goodwill, net	149,900
Power Generation and Industrial [Member]
Goodwill [Line Items]
Goodwill, gross carrying amount	117,600
Goodwill, accumulated impairment losses	0
Goodwill, net	$ 117,600