Financial Data of Business Segments (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) Segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Segment Reporting Information [Line Items]
Provision for Income Taxes, Equity Method Investment									$ (0.5)	$ 18.3	$ 16.5
Number of business segments | Segment									4
Profitability
Lease revenue									$ 1,130.1	1,086.6	975.2
Marine operating revenue									235.0	286.3	275.1
Other revenue									84.8	78.1	70.7
Total Revenues	$ 378.7	$ 386.2	$ 365.3	$ 319.7	$ 401.4	$ 397.2	$ 365.8	$ 286.6	1,449.9	1,451.0	1,321.0
Maintenance expense									326.1	337.0	294.0
Marine operating expense									155.9	197.8	189.8
Depreciation									290.5	273.5	255.0
Operating lease expense									87.2	108.7	129.4
Other operating expense									38.4	28.9	26.1
Total Expenses									898.1	945.9	894.3
Net gain on asset dispositions									79.2	87.2	85.6
Interest expense, net									(155.1)	(158.4)	(166.6)
Other (expense) income									(13.2)	(13.5)	(8.4)
Share of affiliates' earnings (pre-tax)									45.4	67.8	92.3
Segment profit (loss)									508.1	488.2	429.6
SG&A									192.4	189.2	178.3
Income tax benefit									110.9	75.7	65.5
Net Income	58.2	$ 39.5	$ 45.4	$ 62.2	58.5	$ 51.3	$ 53.1	$ 42.1	205.3	205.0	169.3
Disposition Gains on Owned Assets									90.3	63.1	60.0
Nonoperating Income, Residual Sharing Income									13.4	9.4	10.8
Nonremarketing Disposition Gain (Loss)									9.4	16.0	20.7
Asset Impairment Charges									(33.9)	(1.3)	(5.9)
Selected Balance Sheet Data
Investments in affiliated companies	348.5				357.7				348.5	357.7	354.3
Identifiable assets	6,894.2				6,919.9				6,894.2	6,919.9	6,535.5
Capital Expenditures
Portfolio investments and capital additions									$ (714.7)	(1,030.5)	(859.6)
Rail North America [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									5
Profitability
Lease revenue									$ 930.9	864.1	758.9
Marine operating revenue									0.0	0.0	0.0
Other revenue									75.9	63.4	58.2
Total Revenues									1,006.8	927.5	817.1
Maintenance expense									264.2	265.5	228.2
Marine operating expense									0.0	0.0	0.0
Depreciation									215.1	190.0	176.7
Operating lease expense									82.2	103.7	124.4
Other operating expense									26.2	21.9	18.4
Total Expenses									587.7	581.1	547.7
Net gain on asset dispositions									67.2	72.3	67.7
Interest expense, net									(102.1)	(98.4)	(106.0)
Other (expense) income									(5.2)	(7.2)	(9.8)
Share of affiliates' earnings (pre-tax)									0.5	7.9	10.3
Segment profit (loss)									379.5	321.0	231.6
Disposition Gains on Owned Assets									66.6	57.4	51.1
Nonoperating Income, Residual Sharing Income									0.8	5.2	3.4
Nonremarketing Disposition Gain (Loss)									2.3	10.4	14.5
Asset Impairment Charges									(2.5)	(0.7)	(1.3)
Selected Balance Sheet Data
Investments in affiliated companies	12.0				17.2				12.0	17.2	31.4
Identifiable assets	4,629.1				4,358.2				4,629.1	4,358.2	3,710.3
Capital Expenditures
Portfolio investments and capital additions									$ (524.5)	(810.6)	(502.4)
Rail International [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									2
Profitability
Lease revenue									$ 172.9	188.6	180.2
Marine operating revenue									0.0	0.0	0.0
Other revenue									7.5	10.3	8.8
Total Revenues									180.4	198.9	189.0
Maintenance expense									39.6	45.9	42.9
Marine operating expense									0.0	0.0	0.0
Depreciation									43.7	47.1	43.2
Operating lease expense									0.0	0.0	0.0
Other operating expense									5.1	5.1	5.3
Total Expenses									88.4	98.1	91.4
Net gain on asset dispositions									6.8	6.0	3.7
Interest expense, net									(22.4)	(24.7)	(23.9)
Other (expense) income									(6.0)	(3.1)	(1.1)
Share of affiliates' earnings (pre-tax)									(0.3)	(0.3)	21.1
Segment profit (loss)									70.1	78.7	97.4
Disposition Gains on Owned Assets									0.0	0.6	0.3
Nonoperating Income, Residual Sharing Income									0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)									7.2	5.7	6.2
Asset Impairment Charges									(0.4)	(0.3)	(2.8)
Selected Balance Sheet Data
Investments in affiliated companies	1.4				1.8				1.4	1.8	2.0
Identifiable assets	1,117.6				1,228.8				1,117.6	1,228.8	1,296.2
Capital Expenditures
Portfolio investments and capital additions									$ (148.0)	(163.6)	(168.5)
ASC [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									1.5
Profitability
Lease revenue									$ 4.1	4.2	4.2
Marine operating revenue									166.1	223.0	223.5
Other revenue									0.0	0.0	0.0
Total Revenues									170.2	227.2	227.7
Maintenance expense									22.3	25.6	22.9
Marine operating expense									107.2	149.2	151.3
Depreciation									14.3	13.6	12.1
Operating lease expense									5.2	5.2	5.2
Other operating expense									0.0	0.0	0.0
Total Expenses									149.0	193.6	191.5
Net gain on asset dispositions									(0.1)	(0.5)	(1.3)
Interest expense, net									(5.3)	(5.6)	(6.2)
Other (expense) income									(0.7)	(0.2)	0.2
Share of affiliates' earnings (pre-tax)									0.0	0.0	0.0
Segment profit (loss)									15.1	27.3	28.9
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)									(0.1)	(0.1)	0.0
Asset Impairment Charges									0.0	(0.4)	(1.3)
Selected Balance Sheet Data
Investments in affiliated companies	0.0				0.0				0.0	0.0	0.0
Identifiable assets	284.7				286.7				284.7	286.7	271.0
Capital Expenditures
Portfolio investments and capital additions									$ (20.3)	(18.4)	(11.2)
Portfolio Management [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									3
Profitability
Lease revenue									$ 22.2	29.7	31.9
Marine operating revenue									68.9	63.3	51.6
Other revenue									1.4	4.4	3.7
Total Revenues									92.5	97.4	87.2
Maintenance expense									0.0	0.0	0.0
Marine operating expense									48.7	48.6	38.5
Depreciation									17.4	22.8	23.0
Operating lease expense									0.0	0.0	0.0
Other operating expense									7.1	1.9	2.4
Total Expenses									73.2	73.3	63.9
Net gain on asset dispositions									5.3	9.4	15.5
Interest expense, net									(20.0)	(24.3)	(26.7)
Other (expense) income									0.0	(1.2)	1.4
Share of affiliates' earnings (pre-tax)									45.2	60.2	60.9
Segment profit (loss)									49.8	68.2	74.4
Disposition Gains on Owned Assets									23.7	5.1	8.6
Nonoperating Income, Residual Sharing Income									12.6	4.2	7.4
Nonremarketing Disposition Gain (Loss)									0.0	0.0	0.0
Asset Impairment Charges									(31.0)	0.1	(0.5)
Selected Balance Sheet Data
Investments in affiliated companies	335.1				338.7				335.1	338.7	320.9
Identifiable assets	636.5				813.3				636.5	813.3	856.9
Capital Expenditures
Portfolio investments and capital additions									(18.4)	(32.3)	(170.5)
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									(0.2)	(0.2)	(0.2)
Other operating expense									0.0	0.0	0.0
Total Expenses									(0.2)	(0.2)	(0.2)
Net gain on asset dispositions									0.0	0.0	0.0
Interest expense, net									(5.3)	(5.4)	(3.8)
Other (expense) income									(1.3)	(1.8)	0.9
Share of affiliates' earnings (pre-tax)									0.0	0.0	0.0
Segment profit (loss)									(6.4)	(7.0)	(2.7)
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	$ 226.3				$ 232.9				226.3	232.9	401.1
Capital Expenditures
Portfolio investments and capital additions									(3.5)	(5.6)	(7.0)
Parent [Member]
Profitability
Income tax benefit									110.4	$ 94.0	$ 82.0
Cardinal Marine [Domain]
Profitability
Asset Impairment Charges									19.0
Cardinal Marine [Domain] | Portfolio Management [Member]
Profitability
Asset Impairment Charges									$ 19.0