Segments and Related Information (Schedule of Financial Information by Reportable Segment - Depreciation and Amortization) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Depreciation and Amortization:
Depreciation	$ 297.8	$ 235.5	$ 212.9
Reportable Segments [Member] | Communications [Member]
Depreciation and Amortization:
Depreciation	87.1	65.0	59.3
Reportable Segments [Member] | Clean Energy and Infrastructure
Depreciation and Amortization:
Depreciation	18.2	14.1	13.7
Reportable Segments [Member] | Oil and Gas [Member]
Depreciation and Amortization:
Depreciation	156.6	127.2	113.7
Reportable Segments [Member] | Electrical Transmission [Member]
Depreciation and Amortization:
Depreciation	24.7	20.0	19.8
Reportable Segments [Member] | Other [Member]
Depreciation and Amortization:
Depreciation	0.1	0.1	0.1
Corporate [Member]
Depreciation and Amortization:
Depreciation	$ 11.1	$ 9.1	$ 6.3