Goodwill and Other Intangible Assets (Schedule of Goodwill by Segment) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill, gross carrying amount	$ 1,070,800
Accumulated impairment losses	(72,700)
Goodwill, net	998,089	$ 988,511
Communications [Member]
Goodwill [Line Items]
Goodwill, gross carrying amount	420,700
Accumulated impairment losses	0
Goodwill, net	420,700
Oil and Gas [Member]
Goodwill [Line Items]
Goodwill, gross carrying amount	382,600
Accumulated impairment losses	(72,700)
Goodwill, net	309,900
Electrical Transmission [Member]
Goodwill [Line Items]
Goodwill, gross carrying amount	149,900
Accumulated impairment losses	0
Goodwill, net	149,900
Power Generation and Industrial [Member]
Goodwill [Line Items]
Goodwill, gross carrying amount	117,600
Accumulated impairment losses	0
Goodwill, net	$ 117,600