Segments and Related Information (Schedule of Financial Information by Reportable Segment - Depreciation and Amortization) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2014	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Depreciation and Amortization:
Depreciation and amortization	$ 41,747	$ 36,755	$ 33,494	$ 70,249	$ 111,996	$ 154,452	$ 140,926	$ 91,958
Reportable Segments [Member] | Communications [Member]
Depreciation and Amortization:
Depreciation and amortization						42,600	36,800	29,100
Reportable Segments [Member] | Oil and Gas [Member]
Depreciation and Amortization:
Depreciation and amortization						82,800	80,900	42,000
Reportable Segments [Member] | Electrical Transmission [Member]
Depreciation and Amortization:
Depreciation and amortization						17,100	12,600	11,000
Reportable Segments [Member] | Power Generation and Industrial [Member]
Depreciation and Amortization:
Depreciation and amortization						6,400	6,700	6,700
Reportable Segments [Member] | Other [Member]
Depreciation and Amortization:
Depreciation and amortization						0	0	100
Corporate [Member]
Depreciation and Amortization:
Depreciation and amortization						$ 5,600	$ 3,900	$ 3,100