Segments and Related Information (Schedule of Financial Information by Reportable Segment - EBITDA) (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
EBITDA:
EBITDA				$ 823.4	$ 660.8	$ 620.9
Intangible asset, pre-tax impairment charge				3.3
Goodwill, pre-tax impairment charge		$ 47.7			47.7
Joint Venture [Member]
EBITDA:
Project gains (in dollars)			$ (1.0)		(1.0)
Project losses (in dollars)						7.9
Communications [Member]
EBITDA:
Goodwill, pre-tax impairment charge					0.0
Oil and Gas [Member]
EBITDA:
Goodwill, pre-tax impairment charge					47.7
Electrical Transmission [Member]
EBITDA:
Goodwill, pre-tax impairment charge					0.0
Power Generation and Industrial [Member]
EBITDA:
Goodwill, pre-tax impairment charge					0.0
Reportable Segments [Member] | Communications [Member]
EBITDA:
EBITDA				208.8	290.4	247.4
Reportable Segments [Member] | Oil and Gas [Member]
EBITDA:
EBITDA				634.2	451.6	402.2
Reportable Segments [Member] | Electrical Transmission [Member]
EBITDA:
EBITDA				29.5	10.5	17.6
Reportable Segments [Member] | Power Generation and Industrial [Member]
EBITDA:
EBITDA				40.1	40.4	22.6
Reportable Segments [Member] | Other [Member]
EBITDA:
EBITDA				26.5	24.4	19.8
Corporate [Member]
EBITDA:
EBITDA				(115.7)	$ (156.4)	$ (88.7)
Pre-Qualifications [Member]
EBITDA:
Intangible asset, pre-tax impairment charge	$ 3.3			$ 3.3