Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Revenue (in dollars)	$ 1,709,300	$ 2,016,600	$ 1,939,000	$ 1,518,300	$ 1,917,600	$ 1,977,200	$ 1,617,800	$ 1,396,800	$ 7,183,188	$ 6,909,417	$ 6,606,978
Communications [Member] | Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue									15.00%	14.90%	13.40%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)									$ 2,618,800	$ 2,556,800	$ 2,424,400
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)									3,117,200	3,288,700	3,497,200
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)									413,900	397,300	378,200
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)									1,034,300	665,000	299,900
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)									200	3,500	20,800
Eliminations [Member]
Revenue:
Revenue (in dollars)									$ (1,200)	$ (1,900)	$ (13,500)