Segments and Related Information (Schedule of Financial Information by Reportable Segment - Depreciation and Amortization) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Depreciation and Amortization:
Depreciation and amortization	$ 42,598	$ 33,494
Reportable Segments [Member] | Communications [Member]
Depreciation and Amortization:
Depreciation and amortization	12,000	9,900
Reportable Segments [Member] | Oil and Gas [Member]
Depreciation and Amortization:
Depreciation and amortization	22,000	18,100
Reportable Segments [Member] | Electrical Transmission [Member]
Depreciation and Amortization:
Depreciation and amortization	5,200	2,800
Reportable Segments [Member] | Power Generation and Industrial [Member]
Depreciation and Amortization:
Depreciation and amortization	1,600	1,500
Reportable Segments [Member] | Other [Member]
Depreciation and Amortization:
Depreciation and amortization	100	0
Corporate [Member]
Depreciation and Amortization:
Depreciation and amortization	$ 1,700	$ 1,200