Segments and Related Information (Schedule of Segment Reporting Information by Segment - Depreciation and Amortization) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Depreciation and amortization	$ 36,755	$ 33,602	$ 70,249	$ 65,355
Reportable Segments [Member] | Communications [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	10,000	9,100	19,900	17,400
Reportable Segments [Member] | Oil and Gas [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	19,900	19,000	38,000	37,700
Reportable Segments [Member] | Electrical Transmission [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	3,900	2,800	6,700	5,200
Reportable Segments [Member] | Power Generation and Industrial [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	1,600	1,700	3,100	3,400
Corporate [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	$ 1,400	$ 1,000	$ 2,500	$ 1,700