Segment Information - Financial information for segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 831.3	$ 877.3
Operating Profit (Loss)	98.6	115.9
Intersegment
Segment Reporting Information [Line Items]
Total revenues	349.1	243.9
Intersegment | Eliminations – Other
Segment Reporting Information [Line Items]
Total revenues	(53.0)	(51.7)
Operating Profit (Loss)	0.1	(1.9)
Intersegment | Eliminations – Lease subsidiary
Segment Reporting Information [Line Items]
Total revenues	(296.1)	(192.2)
Operating Profit (Loss)	(28.7)	(29.4)
Total
Segment Reporting Information [Line Items]
Total revenues	1,180.4	1,121.2
Operating Profit (Loss)	166.7	182.3
Corporate
Segment Reporting Information [Line Items]
Operating Profit (Loss)	(39.5)	(35.1)
Rail Group
Segment Reporting Information [Line Items]
Total revenues	302.4	286.0
Rail Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	296.1	192.3
Rail Group | Total
Segment Reporting Information [Line Items]
Total revenues	598.5	478.3
Operating Profit (Loss)	58.9	50.5
Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	123.4	120.9
Construction Products Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	1.6	2.2
Construction Products Group | Total
Segment Reporting Information [Line Items]
Total revenues	125.0	123.1
Operating Profit (Loss)	19.4	15.5
Inland Barge Group
Segment Reporting Information [Line Items]
Total revenues	30.8	62.7
Inland Barge Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0
Inland Barge Group | Total
Segment Reporting Information [Line Items]
Total revenues	30.8	62.7
Operating Profit (Loss)	(0.7)	6.3
Energy Equipment Group
Segment Reporting Information [Line Items]
Total revenues	199.2	227.8
Energy Equipment Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	27.5	27.6
Energy Equipment Group | Total
Segment Reporting Information [Line Items]
Total revenues	226.7	255.4
Operating Profit (Loss)	21.3	29.6
Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
Total revenues	174.3	178.6
Railcar Leasing and Management Services Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	0.3	0.3
Railcar Leasing and Management Services Group | Total
Segment Reporting Information [Line Items]
Total revenues	174.6	178.9
Operating Profit (Loss)	71.1	85.0
All Other
Segment Reporting Information [Line Items]
Total revenues	1.2	1.3
All Other | Intersegment
Segment Reporting Information [Line Items]
Total revenues	23.6	21.5
All Other | Total
Segment Reporting Information [Line Items]
Total revenues	24.8	22.8
Operating Profit (Loss)	(3.3)	(4.6)
Railcars | Rail Group
Segment Reporting Information [Line Items]
Total revenues	521.1	425.1
Components and maintenance services | Rail Group
Segment Reporting Information [Line Items]
Total revenues	77.4	53.2
Highway products | Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	54.8	63.5
Construction aggregates | Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	52.6	49.6
Other | Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	17.6	10.0
Other | Energy Equipment Group
Segment Reporting Information [Line Items]
Total revenues	79.2	74.6
Wind towers and utility structures | Energy Equipment Group
Segment Reporting Information [Line Items]
Total revenues	147.5	180.8
Leasing and management | Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
Total revenues	174.6	178.9
Leasing and management | Railcar Leasing and Management Services Group | Total
Segment Reporting Information [Line Items]
Total revenues	174.6	178.9
Operating Profit (Loss)	69.0	85.0
Railcars owned one year or less at the time of sale | Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0
Railcars owned one year or less at the time of sale | Railcar Leasing and Management Services Group | Total
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0
Operating Profit (Loss)	$ 0.0	$ 0.0