Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenue:
Revenue (in dollars)		$ 1,111,010	$ 1,315,488	$ 3,180,906	$ 3,380,538
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue		11.20%	7.60%	10.50%	7.00%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	[1]	$ 513,300	$ 505,200	$ 1,452,100	$ 1,480,400
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)		406,900	554,400	1,144,200	1,299,300
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)		75,900	138,400	270,200	329,100
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)		115,000	114,300	302,300	263,100
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)		3,800	4,100	17,200	10,600
Eliminations [Member]
Revenue:
Revenue (in dollars)		$ (3,900)	$ (900)	$ (5,100)	$ (2,000)

[1] Revenue generated by utilities customers represented 11.2% and 7.6% of Communications segment revenue for the three month periods ended September 30, 2015 and 2014, respectively, and represented 10.5% and 7.0% for the nine month periods ended September 30, 2015 and 2014, respectively.