Segments and Related Information (Schedule of Segment Reporting Information, by Segment - Depreciation and Amortization) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Depreciation and amortization	$ 33,494	$ 31,753
Operating Segments [Member] | Communications [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	9,900	8,200
Operating Segments [Member] | Oil and Gas [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	18,100	18,700
Operating Segments [Member] | Electrical Transmission [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	2,800	2,300
Operating Segments [Member] | Power Generation and Industrial [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	1,500	1,700
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	$ 1,200	$ 900