Segments and Related Information (Schedule of Financial Information by Reportable Segment - Depreciation and Amortization) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Depreciation and Amortization:
Depreciation and amortization	$ 42,196	$ 41,747	$ 128,048	$ 111,996
Reportable Segments [Member] | Communications [Member]
Depreciation and Amortization:
Depreciation and amortization	13,200	10,100	37,600	30,100
Reportable Segments [Member] | Oil and Gas [Member]
Depreciation and Amortization:
Depreciation and amortization	20,000	23,300	64,300	61,300
Reportable Segments [Member] | Electrical Transmission [Member]
Depreciation and Amortization:
Depreciation and amortization	5,500	5,200	16,000	11,900
Reportable Segments [Member] | Power Generation and Industrial [Member]
Depreciation and Amortization:
Depreciation and amortization	1,700	1,700	5,000	4,800
Reportable Segments [Member] | Other [Member]
Depreciation and Amortization:
Depreciation and amortization	0	0	100	0
Corporate [Member]
Depreciation and Amortization:
Depreciation and amortization	$ 1,800	$ 1,400	$ 5,000	$ 3,900