Financial Data of Business Segments (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) Segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Provision for Income Taxes, Equity Method Investment									$ 5.7	$ (0.5)	$ 18.3
Number of business segments | Segment									4
Profitability
Lease revenue									$ 1,127.1	1,130.1	1,086.6
Marine operating revenue									199.3	235.0	286.3
Other revenue									91.9	84.8	78.1
Total Revenues	$ 362.1	$ 362.9	$ 358.9	$ 334.4	$ 378.7	$ 386.2	$ 365.3	$ 319.7	1,418.3	1,449.9	1,451.0
Maintenance expense									332.3	326.1	337.0
Marine operating expense									129.5	155.9	197.8
Depreciation									297.2	290.5	273.5
Operating lease expense									73.5	87.2	108.7
Other operating expense									43.8	38.4	28.9
Total Expenses									876.3	898.1	945.9
Net gain on asset dispositions									98.0	79.2	87.2
Interest expense, net									(148.1)	(155.1)	(158.4)
Other (expense) income									(11.8)	(13.2)	(13.5)
Share of affiliates' earnings (pre-tax)									53.1	45.4	67.8
Segment profit (loss)									533.2	508.1	488.2
SG&A									174.7	192.4	189.2
Income tax benefit									95.7	110.9	75.7
Net Income	30.9	95.7	$ 61.2	$ 69.3	58.2	39.5	$ 45.4	$ 62.2	257.1	205.3	205.0
Disposition Gains on Owned Assets									49.7	90.3	63.1
Nonoperating Income, Residual Sharing Income									83.6	13.4	9.4
Nonremarketing Disposition Gain (Loss)									3.2	9.4	16.0
Asset Impairment Charges									38.5	33.9	1.3
Selected Balance Sheet Data
Investments in affiliated companies	387.0				348.5				387.0	348.5	357.7
Identifiable assets	7,105.4				6,894.2				7,105.4	6,894.2	6,919.9
Capital Expenditures
Portfolio investments and capital additions									$ (620.7)	$ (714.7)	$ (1,030.5)
Rail North America [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									5	5	5
Profitability
Lease revenue									$ 935.1	$ 930.9	$ 864.1
Marine operating revenue									0.0	0.0	0.0
Other revenue									83.4	75.9	63.4
Total Revenues									1,018.5	1,006.8	927.5
Maintenance expense									266.5	264.2	265.5
Marine operating expense									0.0	0.0	0.0
Depreciation									231.8	215.1	190.0
Operating lease expense									67.6	82.2	103.7
Other operating expense									34.1	26.2	21.9
Total Expenses									600.0	587.7	581.1
Net gain on asset dispositions									16.6	67.2	72.3
Interest expense, net									(110.1)	(102.1)	(98.4)
Other (expense) income									(3.6)	(5.2)	(7.2)
Share of affiliates' earnings (pre-tax)									0.5	0.5	7.9
Segment profit (loss)									321.9	379.5	321.0
Disposition Gains on Owned Assets									45.5	66.6	57.4
Nonoperating Income, Residual Sharing Income									0.8	0.8	5.2
Nonremarketing Disposition Gain (Loss)									1.5	2.3	10.4
Asset Impairment Charges									31.2	2.5	0.7
Selected Balance Sheet Data
Investments in affiliated companies	10.5				12.0				10.5	12.0	17.2
Identifiable assets	4,775.6				4,629.1				4,775.6	4,629.1	4,358.2
Capital Expenditures
Portfolio investments and capital additions									$ (495.6)	$ (524.5)	$ (810.6)
Rail International [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									3	2	2
Profitability
Lease revenue									$ 182.0	$ 172.9	$ 188.6
Marine operating revenue									0.0	0.0	0.0
Other revenue									7.0	7.5	10.3
Total Revenues									189.0	180.4	198.9
Maintenance expense									47.2	39.6	45.9
Marine operating expense									0.0	0.0	0.0
Depreciation									45.5	43.7	47.1
Operating lease expense									0.0	0.0	0.0
Other operating expense									5.3	5.1	5.1
Total Expenses									98.0	88.4	98.1
Net gain on asset dispositions									1.1	6.8	6.0
Interest expense, net									(29.7)	(22.4)	(24.7)
Other (expense) income									0.8	(6.0)	(3.1)
Share of affiliates' earnings (pre-tax)									(0.2)	(0.3)	(0.3)
Segment profit (loss)									63.0	70.1	78.7
Disposition Gains on Owned Assets									0.0	0.0	0.6
Nonoperating Income, Residual Sharing Income									0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)									1.7	7.2	5.7
Asset Impairment Charges									0.6	0.4	0.3
Selected Balance Sheet Data
Investments in affiliated companies	1.2				1.4				1.2	1.4	1.8
Identifiable assets	1,128.7				1,117.6				1,128.7	1,117.6	1,228.8
Capital Expenditures
Portfolio investments and capital additions									$ (87.1)	$ (148.0)	$ (163.6)
ASC [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									1.5	1.5	1.5
Profitability
Lease revenue									$ 4.2	$ 4.1	$ 4.2
Marine operating revenue									150.0	166.1	223.0
Other revenue									0.0	0.0	0.0
Total Revenues									154.2	170.2	227.2
Maintenance expense									18.6	22.3	25.6
Marine operating expense									96.7	107.2	149.2
Depreciation									12.9	14.3	13.6
Operating lease expense									6.0	5.2	5.2
Other operating expense									0.0	0.0	0.0
Total Expenses									134.2	149.0	193.6
Net gain on asset dispositions									0.0	(0.1)	(0.5)
Interest expense, net									(4.5)	(5.3)	(5.6)
Other (expense) income									(5.4)	(0.7)	(0.2)
Share of affiliates' earnings (pre-tax)									0.0	0.0	0.0
Segment profit (loss)									10.1	15.1	27.3
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	(0.1)	(0.1)
Asset Impairment Charges									0.0	0.0	0.4
Selected Balance Sheet Data
Investments in affiliated companies	0.0				0.0				0.0	0.0	0.0
Identifiable assets	278.8				284.7				278.8	284.7	286.7
Capital Expenditures
Portfolio investments and capital additions									$ (9.1)	$ (20.3)	$ (18.4)
Portfolio Management [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									1	3	3
Profitability
Lease revenue									$ 5.8	$ 22.2	$ 29.7
Marine operating revenue									49.3	68.9	63.3
Other revenue									1.5	1.4	4.4
Total Revenues									56.6	92.5	97.4
Maintenance expense									0.0	0.0	0.0
Marine operating expense									32.8	48.7	48.6
Depreciation									7.0	17.4	22.8
Operating lease expense									0.0	0.0	0.0
Other operating expense									4.4	7.1	1.9
Total Expenses									44.2	73.2	73.3
Net gain on asset dispositions									80.3	5.3	9.4
Interest expense, net									(8.6)	(20.0)	(24.3)
Other (expense) income									0.0	0.0	(1.2)
Share of affiliates' earnings (pre-tax)									52.8	45.2	60.2
Segment profit (loss)									136.9	49.8	68.2
Disposition Gains on Owned Assets									4.2	23.7	5.1
Nonoperating Income, Residual Sharing Income		$ 30.3							82.8	12.6	4.2
Nonremarketing Disposition Gain (Loss)									0.0	0.0	0.0
Asset Impairment Charges									6.7	31.0	(0.1)
Selected Balance Sheet Data
Investments in affiliated companies	375.3				335.1				375.3	335.1	338.7
Identifiable assets	593.5				636.5				593.5	636.5	813.3
Capital Expenditures
Portfolio investments and capital additions									(25.0)	(18.4)	(32.3)
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									(0.1)	(0.2)	(0.2)
Other operating expense									0.0	0.0	0.0
Total Expenses									(0.1)	(0.2)	(0.2)
Net gain on asset dispositions									0.0	0.0	0.0
Interest expense, net									4.8	(5.3)	(5.4)
Other (expense) income									(3.6)	(1.3)	(1.8)
Share of affiliates' earnings (pre-tax)									0.0	0.0	0.0
Segment profit (loss)									1.3	(6.4)	(7.0)
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	$ 328.8				$ 226.3				328.8	226.3	232.9
Capital Expenditures
Portfolio investments and capital additions									(3.9)	(3.5)	(5.6)
Parent [Member]
Profitability
Income tax benefit									$ 101.4	110.4	$ 94.0
Cardinal Marine [Domain]
Profitability
Asset Impairment Charges						$ 19.0				19.0
Cardinal Marine [Domain] | Portfolio Management [Member]
Profitability
Asset Impairment Charges										$ 19.0