Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue:
Revenue (in dollars)		$ 1,066,629	$ 1,107,232	$ 2,069,896	$ 2,065,050
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue		11.40%	6.30%	10.10%	6.60%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	[1]	$ 468,900	$ 528,100	$ 938,800	$ 975,200
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)		410,500	365,100	737,300	744,900
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)		78,200	116,800	194,300	190,700
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)		103,100	94,500	187,400	148,800
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)		6,900	3,700	13,500	6,500
Eliminations [Member]
Revenue:
Revenue (in dollars)		$ (1,000)	$ (1,000)	$ (1,400)	$ (1,000)

[1] Revenue generated by utilities customers represented 11.4% and 6.3% of Communications segment revenue for the three month periods ended June 30, 2015 and 2014, respectively, and represented 10.1% and 6.6% for the six month periods ended June 30, 2015 and 2014, respectively.