Segments and Related Information (Schedule of Financial Information by Reportable Segment - Capital Expenditures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Capital Expenditures:
Capital expenditures	$ 213,746	$ 126,473	$ 180,420
Reportable Segments [Member] | Communications [Member]
Capital Expenditures:
Capital expenditures	38,400	36,000	69,300
Reportable Segments [Member] | Clean Energy and Infrastructure
Capital Expenditures:
Capital expenditures	14,000	12,700	6,500
Reportable Segments [Member] | Oil and Gas [Member]
Capital Expenditures:
Capital expenditures	149,200	59,700	83,500
Reportable Segments [Member] | Electrical Transmission [Member]
Capital Expenditures:
Capital expenditures	3,800	6,800	10,200
Reportable Segments [Member] | Other [Member]
Capital Expenditures:
Capital expenditures	0	0	0
Corporate [Member]
Capital Expenditures:
Capital expenditures	$ 8,300	$ 11,300	$ 10,900