Segment Information - Financial information for segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 942.3	$ 905.5	$ 1,773.6	$ 1,782.8
Operating Profit (Loss)	125.5	134.6	224.1	250.5
Intersegment
Segment Reporting Information [Line Items]
Total revenues	267.4	178.5	616.5	422.4
Intersegment | Eliminations – Other
Segment Reporting Information [Line Items]
Total revenues	(39.1)	(47.9)	(92.1)	(99.6)
Operating Profit (Loss)	(0.5)	(1.2)	(0.4)	(3.1)
Intersegment | Eliminations – Lease subsidiary
Segment Reporting Information [Line Items]
Total revenues	(228.3)	(130.6)	(524.4)	(322.8)
Operating Profit (Loss)	(24.5)	(14.4)	(53.2)	(43.8)
Total
Segment Reporting Information [Line Items]
Total revenues	1,209.7	1,084.0	2,390.1	2,205.2
Operating Profit (Loss)	193.9	188.6	360.6	370.9
Corporate
Segment Reporting Information [Line Items]
Operating Profit (Loss)	(43.4)	(38.4)	(82.9)	(73.5)
Rail Group
Segment Reporting Information [Line Items]
Total revenues	346.9	335.4	649.3	621.4
Rail Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	228.3	130.5	524.4	322.8
Rail Group | Total
Segment Reporting Information [Line Items]
Total revenues	575.2	465.9	1,173.7	944.2
Operating Profit (Loss)	57.7	36.7	116.6	87.2
Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	153.4	130.7	276.8	251.6
Construction Products Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	2.2	0.6	3.8	2.8
Construction Products Group | Total
Segment Reporting Information [Line Items]
Total revenues	155.6	131.3	280.6	254.4
Operating Profit (Loss)	31.4	22.2	50.8	37.7
Inland Barge Group
Segment Reporting Information [Line Items]
Total revenues	42.9	33.5	73.7	96.2
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	42.9	33.5	73.7	96.2
Operating Profit (Loss)	2.9	0.5	2.2	6.8
Energy Equipment Group
Segment Reporting Information [Line Items]
Total revenues	183.9	212.2	383.1	440.0
Energy Equipment Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	15.4	26.3	42.9	53.9
Energy Equipment Group | Total
Segment Reporting Information [Line Items]
Total revenues	199.3	238.5	426.0	493.9
Operating Profit (Loss)	13.1	24.1	34.4	53.7
Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
Total revenues	213.2	191.9	387.5	370.5
Railcar Leasing and Management Services Group | Intersegment
Segment Reporting Information [Line Items]
Total revenues	0.2	0.2	0.5	0.5
Railcar Leasing and Management Services Group | Total
Segment Reporting Information [Line Items]
Total revenues	213.4	192.1	388.0	371.0
Operating Profit (Loss)	91.8	110.8	162.9	195.8
All Other
Segment Reporting Information [Line Items]
Total revenues	2.0	1.8	3.2	3.1
All Other | Intersegment
Segment Reporting Information [Line Items]
Total revenues	21.3	20.9	44.9	42.4
All Other | Total
Segment Reporting Information [Line Items]
Total revenues	23.3	22.7	48.1	45.5
Operating Profit (Loss)	(3.0)	(5.7)	(6.3)	(10.3)
Railcars | Rail Group
Segment Reporting Information [Line Items]
Total revenues	483.8	407.3	1,004.9	832.4
Components and maintenance services | Rail Group
Segment Reporting Information [Line Items]
Total revenues	91.4	58.6	168.8	111.8
Highway products | Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	71.7	65.6	126.5	129.1
Construction aggregates | Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	61.1	52.2	113.7	101.8
Other | Construction Products Group
Segment Reporting Information [Line Items]
Total revenues	22.8	13.5	40.4	23.5
Other | Energy Equipment Group
Segment Reporting Information [Line Items]
Total revenues	66.3	72.0	145.5	146.6
Wind towers and utility structures | Energy Equipment Group
Segment Reporting Information [Line Items]
Total revenues	133.0	166.5	280.5	347.3
Leasing and management | Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
Total revenues	184.2	185.0	358.8	363.9
Leasing and management | Railcar Leasing and Management Services Group | Total
Segment Reporting Information [Line Items]
Total revenues	184.2	185.0	358.8	363.9
Operating Profit (Loss)	77.9	85.6	146.9	170.6
Railcars owned one year or less at the time of sale | Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
Total revenues	29.2	7.1	29.2	7.1
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	29.2	7.1	29.2	7.1
Operating Profit (Loss)	$ 4.4	$ 1.5	$ 4.4	$ 1.5