Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue:
Revenue (in dollars)	$ 1,636,800	$ 1,698,300	$ 1,569,300	$ 1,416,600	$ 1,709,300	$ 2,016,600	$ 1,939,000	$ 1,518,300	$ 6,320,975	$ 7,183,188	$ 6,909,417
Communications [Member] | Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue									15.60%	15.00%	14.90%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)									$ 2,512,200	$ 2,618,800	$ 2,556,800
Reportable Segments [Member] | Clean Energy and Infrastructure
Revenue:
Revenue (in dollars)									1,526,900	1,034,300	665,000
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)									1,789,800	3,117,200	3,288,700
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)									506,500	413,900	397,300
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)									600	200	3,500
Eliminations [Member]
Revenue:
Revenue (in dollars)									$ (15,000)	$ (1,200)	$ (1,900)