Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Revenue:
Revenue (in dollars)		$ 1,158,184	$ 974,225
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue		13.40%	10.40%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	[1]	$ 559,500	$ 511,600
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)		455,900	292,700
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)		98,800	86,300
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)		46,600	81,400
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)		1,700	3,400
Eliminations [Member]
Revenue:
Revenue (in dollars)		$ (4,300)	$ (1,200)

[1] Revenue generated primarily by utilities customers represented 13.4% and 10.4% of Communications segment revenue for the three month periods ended March 31, 2017 and 2016, respectively.