Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2015	Mar. 31, 2014
Revenue:
Revenue (in dollars)		$ 1,003,268	$ 957,818
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue		8.80%	7.00%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	[1]	$ 469,900	$ 447,100
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)		326,800	379,800
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)		116,000	73,900
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)		84,300	54,200
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)		6,600	2,800
Eliminations [Member]
Revenue:
Revenue (in dollars)		$ (300)	$ 0

[1] Revenue generated by utilities customers represented 8.8% and 7.0% of Communications segment revenue for the three month periods ended March 31, 2015 and 2014, respectively.