Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue:
Revenue (in dollars)	$ 1,569,297	$ 1,939,006	$ 2,985,901	$ 3,457,346
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue	14.90%	15.40%	15.00%	15.50%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	$ 654,300	$ 652,600	$ 1,298,400	$ 1,265,400
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)	368,500	936,800	727,600	1,558,100
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)	124,100	100,400	252,200	195,300
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)	426,100	250,200	712,400	439,600
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)	100	0	100	100
Eliminations [Member]
Revenue:
Revenue (in dollars)	$ (3,800)	$ (1,000)	$ (4,800)	$ (1,200)