Segment Information - Financial information for segments - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 906.4	$ 973.6	$ 905.5	$ 877.3	$ 1,103.8	$ 1,111.7	$ 1,184.9	$ 1,187.9	$ 3,662.8	$ 4,588.3	$ 6,392.7
Operating Profit (Loss)	144.3	$ 153.0	$ 135.2	$ 116.6	163.6	$ 183.6	$ 191.6	$ 203.4	549.1	742.2	1,438.9
Assets	9,543.2				9,125.3				9,543.2	9,125.3	8,885.9
Depreciation & Amortization									295.4	283.0	266.4
Capital Expenditures									712.7	933.4	1,029.8
Intersegment
Segment Reporting Information [Line Items]
Revenues									999.5	1,347.2	1,585.4
Total
Segment Reporting Information [Line Items]
Revenues									4,662.3	5,935.5	7,978.1
Operating Profit (Loss)									815.0	1,052.1	1,852.0
Assets	9,034.0				8,850.9				9,034.0	8,850.9	8,388.8
Depreciation & Amortization									285.9	274.4	258.7
Capital Expenditures									705.1	915.4	1,015.0
Corporate
Segment Reporting Information [Line Items]
Operating Profit (Loss)									(167.3)	(131.0)	(152.6)
Assets	1,320.7				1,079.3				1,320.7	1,079.3	1,175.6
Depreciation & Amortization									9.6	8.7	7.8
Capital Expenditures									7.6	18.0	14.8
Rail Group
Segment Reporting Information [Line Items]
Revenues									1,295.3	2,006.9	3,236.2
Assets	933.0				1,014.1				933.0	1,014.1	1,245.3
Depreciation & Amortization									39.4	41.7	38.8
Capital Expenditures									9.7	29.2	84.0
Rail Group | Intersegment
Segment Reporting Information [Line Items]
Revenues									788.5	1,070.4	1,225.6
Rail Group | Total
Segment Reporting Information [Line Items]
Revenues									2,083.8	3,077.3	4,461.8
Operating Profit (Loss)									216.1	459.9	931.6
Construction Products Group
Segment Reporting Information [Line Items]
Revenues									498.9	510.6	520.6
Assets	571.8				470.3				571.8	470.3	445.1
Depreciation & Amortization									24.6	23.8	24.1
Capital Expenditures									55.5	49.9	28.1
Construction Products Group | Intersegment
Segment Reporting Information [Line Items]
Revenues									5.7	12.6	12.0
Construction Products Group | Total
Segment Reporting Information [Line Items]
Revenues									504.6	523.2	532.6
Operating Profit (Loss)									66.4	72.6	54.5
Inland Barge Group
Segment Reporting Information [Line Items]
Revenues									157.9	403.0	652.9
Assets	111.9				120.8				111.9	120.8	157.7
Depreciation & Amortization									7.3	8.4	10.5
Capital Expenditures									0.3	3.2	5.8
Inland Barge Group | Intersegment
Segment Reporting Information [Line Items]
Revenues									0.0	0.1	0.0
Inland Barge Group | Total
Segment Reporting Information [Line Items]
Revenues									157.9	403.1	652.9
Operating Profit (Loss)									6.4	45.3	117.0
Energy Equipment Group
Segment Reporting Information [Line Items]
Revenues									859.4	834.7	883.6
Assets	1,033.5				1,035.7				1,033.5	1,035.7	1,118.3
Depreciation & Amortization									34.3	36.6	38.2
Capital Expenditures									28.5	25.0	53.5
Energy Equipment Group | Intersegment
Segment Reporting Information [Line Items]
Revenues									115.5	178.0	230.1
Energy Equipment Group | Total
Segment Reporting Information [Line Items]
Revenues									974.9	1,012.7	1,113.7
Operating Profit (Loss)									100.9	133.1	150.9
Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
Revenues									842.2	824.9	1,091.6
Assets	6,267.9				6,095.7				6,267.9	6,095.7	5,358.2
Depreciation & Amortization									172.3	156.2	142.3
Capital Expenditures									608.3	799.1	833.8
Railcar Leasing and Management Services Group | Intersegment
Segment Reporting Information [Line Items]
Revenues									1.0	2.1	13.2
Railcar Leasing and Management Services Group | Total
Segment Reporting Information [Line Items]
Revenues									843.2	827.0	1,104.8
Operating Profit (Loss)									444.5	360.1	606.2
Depreciation & Amortization									172.3	156.2	142.3
All Other
Segment Reporting Information [Line Items]
Revenues									9.1	8.2	7.8
Assets	115.9				114.3				115.9	114.3	64.2
Depreciation & Amortization									8.0	7.7	4.8
Capital Expenditures									2.8	9.0	9.8
All Other | Intersegment
Segment Reporting Information [Line Items]
Revenues									88.8	84.0	104.5
All Other | Total
Segment Reporting Information [Line Items]
Revenues									97.9	92.2	112.3
Operating Profit (Loss)									(19.3)	(18.9)	(8.2)
Eliminations - Lease subsidiary
Segment Reporting Information [Line Items]
Assets	(800.7)				(798.1)				(800.7)	(798.1)	(673.0)
Depreciation & Amortization									0.0	0.0	0.0
Capital Expenditures									0.0	0.0	0.0
Eliminations - Lease subsidiary | Intersegment
Segment Reporting Information [Line Items]
Revenues									(732.0)	(1,021.9)	(1,164.4)
Operating Profit (Loss)									(92.0)	(178.2)	(259.6)
Eliminations - Other
Segment Reporting Information [Line Items]
Assets	$ (10.8)				$ (6.8)				(10.8)	(6.8)	(5.5)
Depreciation & Amortization									(0.1)	(0.1)	(0.1)
Capital Expenditures									0.0	0.0	0.0
Eliminations - Other | Intersegment
Segment Reporting Information [Line Items]
Revenues									(267.5)	(325.3)	(421.0)
Operating Profit (Loss)									$ (6.6)	$ (0.7)	$ (0.9)