Segments and Related Information (Schedule of Financial Information by Reportable Segment - EBITDA) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
EBITDA:
EBITDA	$ 620.9	$ 441.5	$ 150.0
Reportable Segments [Member] | Communications [Member]
EBITDA:
EBITDA	247.4	244.6	194.8
Reportable Segments [Member] | Oil and Gas [Member]
EBITDA:
EBITDA	402.2	297.3	157.0
Reportable Segments [Member] | Electrical Transmission [Member]
EBITDA:
EBITDA	17.6	(42.9)	(71.3)
Reportable Segments [Member] | Power Generation and Industrial [Member]
EBITDA:
EBITDA	22.6	18.3	8.8
Reportable Segments [Member] | Other [Member]
EBITDA:
EBITDA	19.8	(2.6)	(18.8)
Corporate [Member]
EBITDA:
EBITDA	$ (88.7)	$ (73.1)	$ (120.5)