Segments and Related Information (Schedule of Financial Information by Reportable Segment - EBITDA) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
EBITDA:
EBITDA	$ 222.8	$ 175.3	$ 516.1	$ 497.7
Reportable Segments [Member] | Communications [Member]
EBITDA:
EBITDA	74.8	65.3	230.6	173.2
Reportable Segments [Member] | Oil and Gas [Member]
EBITDA:
EBITDA	155.8	108.1	311.5	356.1
Reportable Segments [Member] | Electrical Transmission [Member]
EBITDA:
EBITDA	3.1	4.5	5.0	11.2
Reportable Segments [Member] | Power Generation and Industrial [Member]
EBITDA:
EBITDA	9.7	9.3	24.3	14.8
Reportable Segments [Member] | Other [Member]
EBITDA:
EBITDA	7.0	10.1	19.7	11.6
Corporate [Member]
EBITDA:
EBITDA	$ (27.6)	$ (22.0)	$ (75.0)	$ (69.2)