Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue:
Revenue (in dollars)		$ 1,955,752	$ 1,586,181	$ 5,004,116	$ 3,792,811
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue		13.00%	11.10%	12.60%	10.90%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	[1]	$ 610,500	$ 624,300	$ 1,762,200	$ 1,728,000
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)		1,161,000	736,000	2,757,200	1,454,300
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)		81,800	101,700	277,300	283,600
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)		96,900	123,600	204,100	324,700
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)		10,600	7,600	14,200	14,900
Eliminations [Member]
Revenue:
Revenue (in dollars)		$ (5,000)	$ (7,000)	$ (10,900)	$ (12,700)

[1] Revenue generated primarily by utilities customers represented 13.0% and 11.1% of Communications segment revenue for the three month periods ended September 30, 2017 and 2016, respectively, and represented 12.6% and 10.9% for the nine month periods ended September 30, 2017 and 2016, respectively.