Goodwill - Goodwill by segment (Details) - USD ($) $ in Millions	Mar. 31, 2018		Dec. 31, 2017	[2]
Goodwill [Line Items]
Goodwill	$ 789.8	[1]	$ 780.3
Rail Group
Goodwill [Line Items]
Goodwill	134.6		134.6
Construction Products Group
Goodwill [Line Items]
Goodwill	136.0		136.0
Inland Barge Group
Goodwill [Line Items]
Goodwill	9.9		0.0
Energy Equipment Group
Goodwill [Line Items]
Goodwill	507.5		507.9
Railcar Leasing and Management Services Group
Goodwill [Line Items]
Goodwill	$ 1.8		$ 1.8

[1] (unaudited)

[2] (as reported)