Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Segments and Related Information [Line Items]
Revenue	$ 1,309,596		$ 1,269,385		$ 3,378,180		$ 3,165,657
Reportable Segments [Member] | Communications [Member]
Segments and Related Information [Line Items]
Revenue	505,200	[1]	543,000	[1]	1,480,400	[1]	1,464,500	[1]
Reportable Segments [Member] | Communications [Member] | Utilities [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segments and Related Information [Line Items]
Utilities customers, percentage of consolidated Communications segment revenue	7.60%		6.90%		7.00%		7.20%
Reportable Segments [Member] | Oil and Gas [Member]
Segments and Related Information [Line Items]
Revenue	557,400		519,100		1,302,900		1,134,800
Reportable Segments [Member] | Electrical Transmission [Member]
Segments and Related Information [Line Items]
Revenue	132,600		118,800		327,200		321,900
Reportable Segments [Member] | Power Generation and Industrial [Member]
Segments and Related Information [Line Items]
Revenue	114,300		85,100		263,100		237,300
Reportable Segments [Member] | Other [Member]
Segments and Related Information [Line Items]
Revenue	1,100		3,500		6,500		9,200
Eliminations [Member]
Segments and Related Information [Line Items]
Revenue	$ (1,000)		$ (100)		$ (1,900)		$ (2,000)

[1] Revenue generated by utilities customers represented 7.6% and 6.9% of Communications segment revenue for the three month periods ended September 30, 2014 and 2013, respectively, and 7.0% and 7.2% of Communications segment revenue for the nine month periods ended September 30, 2014 and 2013, respectively.