Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue:
Revenue (in dollars)	$ 1,416,604	$ 1,518,340
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue	15.20%	15.60%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	$ 644,100	$ 612,800
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)	359,100	621,300
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)	128,100	94,900
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)	286,300	189,400
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)	0	0
Eliminations [Member]
Revenue:
Revenue (in dollars)	$ (1,000)	$ (100)