Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenue:
Revenue (in dollars)	$ 974,225	$ 1,003,268
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue	10.40%	8.80%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	$ 511,600	$ 469,900
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)	292,700	326,800
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)	86,300	116,000
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)	81,400	84,300
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)	3,400	6,600
Eliminations [Member]
Revenue:
Revenue (in dollars)	$ (1,200)	$ (300)