Segments and Related Information (Schedule of Financial Information by Reportable Segment - Depreciation and Amortization) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segments and Related Information [Line Items]
Depreciation and amortization	$ 41,747	$ 37,756	$ 111,996	$ 103,111
Reportable Segments [Member] | Communications [Member]
Segments and Related Information [Line Items]
Depreciation and amortization	10,100	9,500	30,100	26,800
Reportable Segments [Member] | Oil and Gas [Member]
Segments and Related Information [Line Items]
Depreciation and amortization	23,300	22,500	61,300	60,100
Reportable Segments [Member] | Electrical Transmission [Member]
Segments and Related Information [Line Items]
Depreciation and amortization	5,200	3,200	11,900	8,400
Reportable Segments [Member] | Power Generation and Industrial [Member]
Segments and Related Information [Line Items]
Depreciation and amortization	1,700	1,700	4,800	5,100
Corporate [Member]
Segments and Related Information [Line Items]
Depreciation and amortization	$ 1,400	$ 900	$ 3,900	$ 2,700