Segments and Related Information (Schedule of Financial Information by Reportable Segment - Depreciation and Amortization) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Depreciation and Amortization:
Depreciation and amortization	$ 39,008	$ 42,598
Reportable Segments [Member] | Communications [Member]
Depreciation and Amortization:
Depreciation and amortization	12,300	12,000
Reportable Segments [Member] | Oil and Gas [Member]
Depreciation and Amortization:
Depreciation and amortization	18,200	22,000
Reportable Segments [Member] | Electrical Transmission [Member]
Depreciation and Amortization:
Depreciation and amortization	5,200	5,200
Reportable Segments [Member] | Power Generation and Industrial [Member]
Depreciation and Amortization:
Depreciation and amortization	1,500	1,600
Reportable Segments [Member] | Other [Member]
Depreciation and Amortization:
Depreciation and amortization	0	100
Corporate [Member]
Depreciation and Amortization:
Depreciation and amortization	$ 1,800	$ 1,700