Goodwill - Goodwill - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 780,300,000	$ 754,100,000
Goodwill by Segment
Goodwill, Impairment Loss	0	0
Rail Group
Goodwill [Line Items]
Goodwill	134,600,000	134,600,000
Construction Products Group
Goodwill [Line Items]
Goodwill	136,000,000	111,000,000
Energy Equipment Group
Goodwill [Line Items]
Goodwill	507,900,000	506,700,000
Railcar Leasing and Management Services Group
Goodwill [Line Items]
Goodwill	$ 1,800,000	$ 1,800,000