Segment Information - Financial information for segments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 930.9	$ 973.6	$ 2,704.5	$ 2,756.4
Operating Profit (Loss)	78.9	152.4	303.0	402.9
Intersegment
Segment Reporting Information [Line Items]
Total revenues	250.1	225.8	866.6	648.2
Intersegment | Eliminations – Other
Segment Reporting Information [Line Items]
Total revenues	(42.7)	(50.8)	(134.8)	(150.4)
Operating Profit (Loss)	0.9	(0.2)	0.5	(3.3)
Intersegment | Eliminations – Lease subsidiary
Segment Reporting Information [Line Items]
Total revenues	(207.4)	(175.0)	(731.8)	(497.8)
Operating Profit (Loss)	(18.1)	(14.6)	(71.3)	(58.4)
Total
Segment Reporting Information [Line Items]
Total revenues	1,181.0	1,199.4	3,571.1	3,404.6
Operating Profit (Loss)	137.6	208.6	498.2	579.5
Corporate
Segment Reporting Information [Line Items]
Operating Profit (Loss)	(41.5)	(41.4)	(124.4)	(114.9)
Rail Group
Segment Reporting Information [Line Items]
Total revenues	299.4	317.4	948.7	938.8
Rail Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	207.4	175.0	731.8	497.8
Rail Group | Total
Segment Reporting Information [Line Items]
Total revenues	506.8	492.4	1,680.5	1,436.6
Operating Profit (Loss)	32.9	50.5	149.5	137.7
Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	148.3	130.1	425.1	381.7
Construction Products Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	3.7	1.8	7.5	4.6
Construction Products Group | Total
Segment Reporting Information [Line Items]
Total revenues	152.0	131.9	432.6	386.3
Operating Profit (Loss)	29.1	16.8	79.9	54.5
Inland Barge Group
Segment Reporting Information [Line Items]
Total revenues	49.3	28.1	123.0	124.3
Inland Barge Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0	0.0	0.0
Inland Barge Group | Total
Segment Reporting Information [Line Items]
Total revenues	49.3	28.1	123.0	124.3
Operating Profit (Loss)	3.0	(0.7)	5.2	6.1
Energy Equipment Group
Segment Reporting Information [Line Items]
Total revenues	203.1	220.6	586.2	660.6
Energy Equipment Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	15.1	25.6	58.0	79.5
Energy Equipment Group | Total
Segment Reporting Information [Line Items]
Total revenues	218.2	246.2	644.2	740.1
Operating Profit (Loss)	(13.7)	26.3	20.7	80.0
Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
Total revenues	227.2	274.9	614.7	645.4
Railcar Leasing and Management Services Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	0.3	0.2	0.8	0.7
Railcar Leasing and Management Services Group | Total
Segment Reporting Information [Line Items]
Total revenues	227.5	275.1	615.5	646.1
Operating Profit (Loss)	92.2	120.6	255.1	316.4
All Other
Segment Reporting Information [Line Items]
Total revenues	3.6	2.5	6.8	5.6
All Other | Intersegment
Segment Reporting Information [Line Items]
Total revenues	23.6	23.2	68.5	65.6
All Other | Total
Segment Reporting Information [Line Items]
Total revenues	27.2	25.7	75.3	71.2
Operating Profit (Loss)	(5.9)	(4.9)	(12.2)	(15.2)
Railcars | Rail Group
Segment Reporting Information [Line Items]
Total revenues	408.2	437.0	1,413.1	1,269.4
Components and maintenance services | Rail Group
Segment Reporting Information [Line Items]
Total revenues	98.6	55.4	267.4	167.2
Highway products | Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	79.4	62.4	205.9	191.5
Construction aggregates | Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	52.9	53.3	166.6	155.1
Other | Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	19.7	16.2	60.1	39.7
Other | Energy Equipment Group
Segment Reporting Information [Line Items]
Total revenues	71.2	79.1	216.7	225.7
Wind towers and utility structures | Energy Equipment Group
Segment Reporting Information [Line Items]
Total revenues	147.0	167.1	427.5	514.4
Leasing and management | Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
Total revenues	175.9	188.5	534.7	552.4
Leasing and management | Railcar Leasing and Management Services Group | Total
Segment Reporting Information [Line Items]
Total revenues	175.9	188.5	534.7	552.4
Operating Profit (Loss)	69.7	86.2	216.6	256.8
Railcars owned one year or less at the time of sale | Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
Total revenues	51.6	86.6	80.8	93.7
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	51.6	86.6	80.8	93.7
Operating Profit (Loss)	$ 13.1	$ 17.9	$ 17.5	$ 19.4