Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue:
Revenue (in dollars)	$ 1,698,279	$ 2,016,618	$ 4,684,180	$ 5,473,965
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue	15.70%	14.90%	15.30%	15.30%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	$ 645,400	$ 679,500	$ 1,943,800	$ 1,944,900
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)	462,500	972,500	1,190,100	2,530,500
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)	128,500	103,000	380,700	298,300
Reportable Segments [Member] | Clean Energy and Infrastructure [Member]
Revenue:
Revenue (in dollars)	468,900	261,700	1,181,400	701,300
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)	100	100	200	100
Eliminations [Member]
Revenue:
Revenue (in dollars)	$ (7,100)	$ (200)	$ (12,000)	$ (1,100)