Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue:
Revenue (in dollars)		$ 1,341,900	$ 1,586,200	$ 1,232,400	$ 974,200	$ 1,027,400	$ 1,111,000	$ 1,066,600	$ 1,003,300	$ 5,134,703	$ 4,208,330	$ 4,611,803
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue										11.10%	10.60%	6.80%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	[1]									$ 2,323,600	$ 1,973,200	$ 2,041,000
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)										2,024,400	1,495,100	1,731,400
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)										383,800	341,500	471,900
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)										405,700	381,600	357,000
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)										15,900	24,100	14,700
Eliminations [Member]
Revenue:
Revenue (in dollars)										$ (18,700)	$ (7,200)	$ (4,200)

[1] Revenue generated primarily by utilities customers represented 11.1%, 10.6% and 6.8% of Communications segment revenue for the years ended December 31, 2016, 2015 and 2014, respectively.