Segments and Related Information (Schedule of Financial Information by Reportable Segment - Depreciation and Amortization) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Depreciation and Amortization:
Depreciation and amortization	$ 40,657	$ 43,254	$ 79,664	$ 85,852
Reportable Segments [Member] | Communications [Member]
Depreciation and Amortization:
Depreciation and amortization	12,400	12,400	24,600	24,400
Reportable Segments [Member] | Oil and Gas [Member]
Depreciation and Amortization:
Depreciation and amortization	19,300	22,300	37,500	44,300
Reportable Segments [Member] | Electrical Transmission [Member]
Depreciation and Amortization:
Depreciation and amortization	5,800	5,200	11,000	10,500
Reportable Segments [Member] | Power Generation and Industrial [Member]
Depreciation and Amortization:
Depreciation and amortization	1,500	1,700	3,100	3,300
Reportable Segments [Member] | Other [Member]
Depreciation and Amortization:
Depreciation and amortization	0	0	0	0
Corporate [Member]
Depreciation and Amortization:
Depreciation and amortization	$ 1,700	$ 1,700	$ 3,500	$ 3,400