Segments and Related Information (Schedule of Financial Information by Reportable Segment - EBITDA) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
EBITDA:
EBITDA	$ 104.6	$ 123.5
Reportable Segments [Member] | Communications [Member]
EBITDA:
EBITDA	82.1	48.4
Reportable Segments [Member] | Oil and Gas [Member]
EBITDA:
EBITDA	33.0	93.9
Reportable Segments [Member] | Electrical Transmission [Member]
EBITDA:
EBITDA	4.6	3.2
Reportable Segments [Member] | Power Generation and Industrial [Member]
EBITDA:
EBITDA	4.8	0.8
Reportable Segments [Member] | Other [Member]
EBITDA:
EBITDA	5.9	(5.3)
Corporate [Member]
EBITDA:
EBITDA	$ (25.8)	$ (17.5)