Goodwill and Other Intangible Assets (Rollforward of Goodwill by Segment) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill, net, beginning balance		$ 988,511	$ 1,082,500
Currency translation adjustments		1,600	(22,700)
Measurement period adjustments	[1]		(3,600)
Goodwill impairment	[2]		(68,500)
Goodwill, net, ending balance		995,874	988,511
Goodwill, accumulated impairment loss	[3]	(69,900)
Goodwill, gross		1,065,800
Earn-Out Arrangements [Member]
Goodwill [Line Items]
Accruals of acquisition-related contingent consideration, net	[4]	5,800	800
Communications [Member]
Goodwill [Line Items]
Goodwill, net, beginning balance		414,900	417,700
Currency translation adjustments		0	0
Measurement period adjustments	[1]		(3,600)
Goodwill impairment	[2]		0
Goodwill, net, ending balance		420,700	414,900
Goodwill, accumulated impairment loss	[3]	0
Goodwill, gross		420,700
Communications [Member] | Earn-Out Arrangements [Member]
Goodwill [Line Items]
Accruals of acquisition-related contingent consideration, net	[4]	5,800	800
Oil and Gas [Member]
Goodwill [Line Items]
Goodwill, net, beginning balance		306,100	397,300
Currency translation adjustments		1,600	(22,700)
Measurement period adjustments	[1]		0
Goodwill impairment	[2]		(68,500)
Goodwill, net, ending balance		307,700	306,100
Goodwill, accumulated impairment loss	[3]	(69,900)
Goodwill, gross		377,600
Oil and Gas [Member] | Earn-Out Arrangements [Member]
Goodwill [Line Items]
Accruals of acquisition-related contingent consideration, net	[4]	0	0
Electrical Transmission [Member]
Goodwill [Line Items]
Goodwill, net, beginning balance		149,900	149,900
Currency translation adjustments		0	0
Measurement period adjustments	[1]		0
Goodwill impairment	[2]		0
Goodwill, net, ending balance		149,900	149,900
Goodwill, accumulated impairment loss	[3]	0
Goodwill, gross		149,900
Electrical Transmission [Member] | Earn-Out Arrangements [Member]
Goodwill [Line Items]
Accruals of acquisition-related contingent consideration, net	[4]	0	0
Power Generation and Industrial [Member]
Goodwill [Line Items]
Goodwill, net, beginning balance		117,600	117,600
Currency translation adjustments		0	0
Measurement period adjustments	[1]		0
Goodwill impairment	[2]		0
Goodwill, net, ending balance		117,600	117,600
Goodwill, accumulated impairment loss	[3]	0
Goodwill, gross		117,600
Power Generation and Industrial [Member] | Earn-Out Arrangements [Member]
Goodwill [Line Items]
Accruals of acquisition-related contingent consideration, net	[4]	$ 0	$ 0

[1] Represent adjustments to preliminary estimates of the fair values of net assets acquired within the measurement period for the WesTower acquisition.

[2] Represents a non-cash goodwill impairment charge related to a reporting unit in western Canada.

[3] Accumulated impairment losses include the effect of currency translation gains and/or losses.

[4] Represents contingent consideration for acquisitions prior to January 1, 2009, which is accrued as incurred, in accordance with U.S. GAAP.