Note 4. Segment Information Segment Information (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment									3
External Revenue									$ 3,005.1	$ 2,509.1	$ 2,397.4
Revenues	$ 850.7	$ 813.6	$ 736.0	$ 604.8	$ 735.0	$ 606.9	$ 634.0	$ 533.2	3,005.1	2,509.1	2,397.4
Operating Income (Loss)	97.2	120.3	107.0	91.8	89.8	75.2	88.0	62.1	416.3	315.1	368.3
Restructuring Charges	(14.7)	0.0	0.0	0.0					(14.7)	0.0	0.0
Other Nonoperating Expense									215.6	163.5	172.9
Income Tax Expense (Benefit)	20.3	18.2	14.1	8.9	17.7	6.7	12.5	5.7	61.5	42.6	(414.8)
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(0.8)	(0.4)	(0.8)	(1.1)	(0.3)	(0.2)	28.2	26.4	(3.1)	54.1	103.4
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	21.5	$ 47.7	$ 36.8	$ 30.1	27.7	$ 28.3	$ 65.5	$ 41.6	136.1	163.1	713.6
Depreciation, Depletion and Amortization									283.6	251.9	229.7
Payments to Acquire Productive Assets									1,219.2	985.6	630.3
Assets	8,701.4				7,989.2				8,701.4	7,989.2
Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
External Revenue									1,116.3	842.0	842.2
Rail Group [Member]
Segment Reporting Information [Line Items]
External Revenue									1,595.4	1,356.4	1,254.5
Other Segments [Member]
Segment Reporting Information [Line Items]
External Revenue									293.4	310.7	300.7
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues									3,005.1	2,509.1	2,397.4
Operating Segments [Member] | Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
Revenues									1,117.2	842.8	843.2
Operating Income (Loss)									406.6	351.1	444.5
Restructuring Charges									(0.2)
Depreciation, Depletion and Amortization									232.2	196.6	172.3
Payments to Acquire Productive Assets									1,122.2	948.3	608.3
Assets	8,012.6				7,096.0				8,012.6	7,096.0
Operating Segments [Member] | Rail Group [Member]
Segment Reporting Information [Line Items]
Revenues									2,926.5	2,346.7	2,044.0
Operating Income (Loss)									281.4	172.1	196.3
Restructuring Charges									(0.7)
Depreciation, Depletion and Amortization									29.6	30.3	35.1
Payments to Acquire Productive Assets									85.6	16.0	4.9
Assets	992.8				1,039.1				992.8	1,039.1
Operating Segments [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues									345.1	361.3	333.1
Operating Income (Loss)									16.1	35.7	1.4
Restructuring Charges									(11.4)
Depreciation, Depletion and Amortization									12.8	15.1	12.8
Payments to Acquire Productive Assets									9.1	17.3	9.5
Assets	222.7				238.5				222.7	238.5
Operating Segments [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)									704.1	558.9	642.2
Assets	9,228.1				8,373.6				9,228.1	8,373.6
Operating Segments [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)									(108.0)	(149.1)	(175.1)
Restructuring Charges									(2.4)
Depreciation, Depletion and Amortization									9.0	9.9	9.6
Payments to Acquire Productive Assets									2.3	4.0	7.6
Assets	378.1				443.4				378.1	443.4
Intersegment Eliminations [Member] | Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues									0.9	0.8	1.0
Intersegment Eliminations [Member] | Rail Group [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues									1,331.1	990.3	789.5
Intersegment Eliminations [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues									51.7	50.6	32.4
MEXICO
Segment Reporting Information [Line Items]
Assets	136.0				116.0				136.0	116.0
Long-Lived Assets	112.2				84.2				112.2	84.2
Consolidated Subsidiaries, Leasing [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues									(1,331.1)	(990.3)	(789.5)
Revenues									(1,331.1)	(990.3)	(789.5)
Operating Income (Loss)									(164.7)	(95.1)	(96.5)
Depreciation, Depletion and Amortization									0.0	0.0	0.0
Payments to Acquire Productive Assets									0.0	0.0	0.0
Assets	(903.8)				(827.7)				(903.8)	(827.7)
Consolidated Subsidiaries, Excluding Leasing [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues									(52.6)	(51.4)	(33.4)
Revenues									(52.6)	(51.4)	(33.4)
Operating Income (Loss)									(0.4)	0.4	(2.3)
Depreciation, Depletion and Amortization									0.0	0.0	(0.1)
Payments to Acquire Productive Assets									0.0	0.0	$ 0.0
Assets	$ (1.0)				$ (0.1)				$ (1.0)	$ (0.1)