Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue:
Revenue (in dollars)		$ 1,890,180	$ 1,232,404	$ 3,048,364	$ 2,206,630
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue		11.50%	11.00%	12.40%	10.70%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	[1]	$ 592,200	$ 592,200	$ 1,151,700	$ 1,103,800
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)		1,140,400	425,600	1,596,200	718,400
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)		96,600	95,600	195,400	181,900
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)		60,700	119,700	107,300	201,100
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)		1,900	3,900	3,600	7,300
Eliminations [Member]
Revenue:
Revenue (in dollars)		$ (1,600)	$ (4,600)	$ (5,800)	$ (5,900)

[1] Revenue generated primarily by utilities customers represented 11.5% and 11.0% of Communications segment revenue for the three month periods ended June 30, 2017 and 2016, respectively, and represented 12.4% and 10.7% for the six month periods ended June 30, 2017 and 2016, respectively.