Financial Data of Business Segments (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) Segment Vessel	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2015
Segment Reporting Information [Line Items]
Provision for Income Taxes, Equity Method Investment									$ 10.8	$ 12.0	$ 5.7
Number of business segments | Segment									4
Profitability
Lease revenue									$ 1,087.8	1,098.1	1,127.1
Marine operating revenue									196.0	193.4	199.3
Other revenue									77.1	85.4	91.9
Total Revenues	$ 356.4	$ 349.7	$ 349.5	$ 305.3	$ 352.8	$ 359.6	$ 348.4	$ 316.1	1,360.9	1,376.9	1,418.3
Maintenance expense									321.8	328.3	332.3
Marine operating expense									130.9	131.0	129.5
Depreciation									321.9	307.3	297.2
Operating lease expense									49.6	62.5	73.5
Other operating expense									33.1	34.4	43.8
Total Expenses									857.3	863.5	876.3
Net gain on asset dispositions									72.8	54.1	98.0
Interest expense, net									(168.6)	(160.5)	(148.1)
Other (expense) income									(21.6)	(12.6)	(17.5)
Share of affiliates' earnings (pre-tax)									61.1	55.9	53.1
Segment profit (loss)									447.3	450.3	527.5
SG&A									191.1	180.0	169.0
Income tax benefit									34.1	(243.7)	95.7
Net Income	49.2	$ 47.0	$ 38.8	$ 76.3	342.1	$ 49.0	$ 53.4	$ 57.5	211.3	502.0	257.1
Disposition Gains on Owned Assets									64.8	44.1	49.7
Nonoperating Income, Residual Sharing Income									2.5	10.2	83.6
Nonremarketing Disposition Gain (Loss)									14.5	8.4	3.2
Asset Impairment Charges									(9.0)	(8.6)	(38.5)
Selected Balance Sheet Data
Investments in affiliated companies	464.5				441.0				464.5	441.0	387.0
Identifiable assets	7,616.7				7,422.4				7,616.7	7,422.4	7,105.4
Capital Expenditures
Portfolio investments and capital additions									$ (943.4)	(603.4)	(620.7)
ASC [Member]
Segment Reporting Information [Line Items]
Number Of Vessels | Vessel									9
Profitability
Lease revenue									$ 4.1	4.1	4.2
Marine operating revenue									181.7	168.4	150.0
Other revenue									0.0	0.0	0.0
Total Revenues									185.8	172.5	154.2
Maintenance expense									22.6	22.2	18.6
Marine operating expense									114.1	106.2	96.7
Depreciation									10.6	12.0	12.9
Operating lease expense									0.0	1.8	6.0
Other operating expense									0.0	0.0	0.0
Total Expenses									147.3	142.2	134.2
Net gain on asset dispositions									0.1	(1.9)	0.0
Interest expense, net									(5.7)	(5.2)	(4.5)
Other (expense) income									0.1	1.3	(5.4)
Share of affiliates' earnings (pre-tax)									0.0	0.0	0.0
Segment profit (loss)									33.0	24.5	10.1
Disposition Gains on Owned Assets									0.1	(1.8)	0.0
Nonoperating Income, Residual Sharing Income									0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)									0.0	(0.1)	0.0
Asset Impairment Charges									0.0	0.0	0.0
Selected Balance Sheet Data
Investments in affiliated companies	0.0				0.0				0.0	0.0	0.0
Identifiable assets	297.8				286.7				297.8	286.7	278.8
Capital Expenditures
Portfolio investments and capital additions									(15.8)	(14.0)	(9.1)
Rail North America [Member]
Profitability
Lease revenue									873.4	899.9	935.1
Marine operating revenue									0.0	0.0	0.0
Other revenue									68.1	77.5	83.4
Total Revenues									941.5	977.4	1,018.5
Maintenance expense									254.7	265.0	266.5
Marine operating expense									0.0	0.0	0.0
Depreciation									248.5	239.4	231.8
Operating lease expense									49.6	60.7	67.6
Other operating expense									27.3	28.7	34.1
Total Expenses									580.1	593.8	600.0
Net gain on asset dispositions									76.3	45.2	16.6
Interest expense, net									(125.2)	(121.2)	(110.1)
Other (expense) income									(5.2)	(5.9)	(3.6)
Share of affiliates' earnings (pre-tax)									0.6	(2.4)	0.5
Segment profit (loss)									307.9	299.3	321.9
Disposition Gains on Owned Assets									64.7	44.0	45.5
Nonoperating Income, Residual Sharing Income									1.4	0.6	0.8
Nonremarketing Disposition Gain (Loss)									10.8	5.2	1.5
Asset Impairment Charges									(0.6)	(4.6)	(31.2)
Selected Balance Sheet Data
Investments in affiliated companies	0.2				6.8				0.2	6.8	10.5
Identifiable assets	5,236.6				4,915.0				5,236.6	4,915.0	4,775.6
Capital Expenditures
Portfolio investments and capital additions									(737.4)	(460.9)	(495.6)
Rail International [Member]
Profitability
Lease revenue									209.3	190.3	182.0
Marine operating revenue									0.0	0.0	0.0
Other revenue									8.2	6.8	7.0
Total Revenues									217.5	197.1	189.0
Maintenance expense									44.5	41.1	47.2
Marine operating expense									0.0	0.0	0.0
Depreciation									55.5	48.9	45.5
Operating lease expense									0.0	0.0	0.0
Other operating expense									5.8	4.7	5.3
Total Expenses									105.8	94.7	98.0
Net gain on asset dispositions									(0.2)	3.1	1.1
Interest expense, net									(35.9)	(33.4)	(29.7)
Other (expense) income									(7.0)	(3.2)	0.8
Share of affiliates' earnings (pre-tax)									0.0	(0.1)	(0.2)
Segment profit (loss)									68.6	68.8	63.0
Disposition Gains on Owned Assets									0.0	0.1	0.0
Nonoperating Income, Residual Sharing Income									0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)									3.7	3.3	1.7
Asset Impairment Charges									(3.9)	(0.3)	(0.6)
Selected Balance Sheet Data
Investments in affiliated companies	0.0				0.0				0.0	0.0	1.2
Identifiable assets	1,363.2				1,332.9				1,363.2	1,332.9	1,128.7
Capital Expenditures
Portfolio investments and capital additions									(152.7)	(90.9)	(87.1)
Portfolio Management [Member]
Profitability
Lease revenue									1.0	3.8	5.8
Marine operating revenue									14.3	25.0	49.3
Other revenue									0.8	1.1	1.5
Total Revenues									16.1	29.9	56.6
Maintenance expense									0.0	0.0	0.0
Marine operating expense									16.8	24.8	32.8
Depreciation									7.3	7.0	7.0
Operating lease expense									0.0	0.0	0.0
Other operating expense									0.0	1.0	4.4
Total Expenses									24.1	32.8	44.2
Net gain on asset dispositions									(3.4)	7.7	80.3
Interest expense, net									(10.4)	(9.2)	(8.6)
Other (expense) income									0.0	2.3	0.0
Share of affiliates' earnings (pre-tax)									60.5	58.4	52.8
Segment profit (loss)									38.7	56.3	136.9
Disposition Gains on Owned Assets									0.0	1.8	4.2
Nonoperating Income, Residual Sharing Income									1.1	9.6	82.8
Nonremarketing Disposition Gain (Loss)									0.0	0.0	0.0
Asset Impairment Charges									(4.5)	(3.7)	(6.7)
Selected Balance Sheet Data
Investments in affiliated companies	464.3				434.2				464.3	434.2	375.3
Identifiable assets	606.8				582.8				606.8	582.8	593.5
Capital Expenditures
Portfolio investments and capital additions									(14.1)	(36.6)	(25.0)
Other [Member]
Profitability
Lease revenue									0.0	0.0	0.0
Marine operating revenue									0.0	0.0	0.0
Other revenue									0.0	0.0	0.0
Total Revenues									0.0	0.0	0.0
Maintenance expense									0.0	0.0	0.0
Marine operating expense									0.0	0.0	0.0
Depreciation									0.0	0.0	0.0
Operating lease expense									0.0	0.0	(0.1)
Other operating expense									0.0	0.0	0.0
Total Expenses									0.0	0.0	(0.1)
Net gain on asset dispositions									0.0	0.0	0.0
Interest expense, net									8.6	8.5	4.8
Other (expense) income									(9.5)	(7.1)	(9.3)
Share of affiliates' earnings (pre-tax)									0.0	0.0	0.0
Segment profit (loss)									(0.9)	1.4	(4.4)
Disposition Gains on Owned Assets									0.0	0.0	0.0
Nonoperating Income, Residual Sharing Income									0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)									0.0	0.0	0.0
Asset Impairment Charges									0.0	0.0	0.0
Selected Balance Sheet Data
Investments in affiliated companies	0.0				0.0				0.0	0.0	0.0
Identifiable assets	$ 112.3				$ 305.0				112.3	305.0	328.8
Capital Expenditures
Portfolio investments and capital additions									(23.4)	(1.0)	(3.9)
Parent [Member]
Profitability
Income tax benefit									$ 44.9	$ (231.7)	$ 101.4
Cardinal Marine [Domain]
Capital Expenditures
Noncontrolling Interest, Ownership Percentage by Parent												50.00%