Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenue:
Revenue (in dollars)		$ 1,232,404	$ 1,066,629	$ 2,206,630	$ 2,069,896
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue		11.00%	11.40%	10.70%	10.10%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	[1]	$ 592,200	$ 468,900	$ 1,103,800	$ 938,800
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)		425,600	410,500	718,400	737,300
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)		95,600	78,200	181,900	194,300
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)		119,700	103,100	201,100	187,400
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)		3,900	6,900	7,300	13,500
Eliminations [Member]
Revenue:
Revenue (in dollars)		$ (4,600)	$ (1,000)	$ (5,900)	$ (1,400)

[1] Revenue generated primarily by utilities customers represented 11.0% and 11.4% of Communications segment revenue for the three month periods ended June 30, 2016 and 2015, respectively, and represented 10.7% and 10.1% for the six month periods ended June 30, 2016 and 2015, respectively.