Financial Data of Business Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Segment	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Provision for Income Taxes, Equity Method Investment	$ 4.6	$ (3.7)	$ 14.2	$ 9.7
Number of business segments			4
Profitability
Lease revenue	279.1	246.7	804.0	722.9
Marine operating revenue	98.9	89.0	188.8	190.8
Other revenue	19.2	17.5	56.8	50.7
Total Revenues	397.2	353.2	1,049.6	964.4
Maintenance expense	85.6	76.9	242.7	217.9
Marine operating expense	64.8	58.2	134.4	132.5
Depreciation	71.9	65.6	201.7	186.6
Operating lease expense	27.4	31.5	81.6	97.4
Other operating expense	8.0	6.9	21.3	19.2
Total Expenses	257.7	239.1	681.7	653.6
Disposition gains on owned assets	1.2	18.2	41.6	35.4
Residual sharing income	1.2	1.8	8.0	9.8
Nonremarketing disposition gains	4.0	3.7	13.4	16.8
Asset impairment	(0.1)	(0.2)	(0.4)	(2.2)
Net gain on asset dispositions	6.3	23.5	62.6	59.8
Interest expense, net	(38.1)	(41.1)	(119.6)	(125.2)
Other (expense) income	(3.1)	(4.4)	(11.4)	(8.6)
Share of affiliates' earnings (pre-tax)	17.0	31.3	48.8	66.6
Segment profit (loss)	121.6	123.4	348.3	303.4
SG&A	45.8	42.0	133.4	129.8
Income tax benefit	19.9	31.3	54.2	47.9
Net Income	51.3	53.8	146.5	116.0
Capital Expenditures
Portfolio investments and capital additions	171.5	196.2	826.6	666.8
Selected Balance Sheet Data
Investments in affiliated companies	348.1		348.1		354.3
Identifiable assets	6,816.3		6,816.3		6,549.6
Rail North America [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity			5
Profitability
Lease revenue	222.6	192.2	635.7	563.3
Marine operating revenue	0	0	0	0
Other revenue	15.7	14.3	46.4	41.9
Total Revenues	238.3	206.5	682.1	605.2
Maintenance expense	65.7	58.6	192.2	170.8
Marine operating expense	0	0	0	0
Depreciation	49.7	44.9	140.3	129.9
Operating lease expense	25.6	29.7	78.2	94.0
Other operating expense	6.1	4.9	16.1	13.9
Total Expenses	147.1	138.1	426.8	408.6
Disposition gains on owned assets	1.2	18.1	40.5	27.0
Residual sharing income	0.1	0.3	4.5	3.2
Nonremarketing disposition gains	3.1	2.2	8.1	11.5
Asset impairment	0	(0.1)	0	(0.8)
Net gain on asset dispositions	4.4	20.5	53.1	40.9
Interest expense, net	(24.1)	(26.1)	(74.0)	(80.5)
Other (expense) income	(1.0)	(4.8)	(4.7)	(8.9)
Share of affiliates' earnings (pre-tax)	0.1	(0.1)	7.6	8.3
Segment profit (loss)	70.6	57.9	237.3	156.4
Capital Expenditures
Portfolio investments and capital additions	(118.9)	(130.8)	(660.7)	(345.9)
Selected Balance Sheet Data
Investments in affiliated companies	18.4		18.4		31.4
Identifiable assets	4,331.0		4,331.0		3,710.5
Rail International [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity			2
Profitability
Lease revenue	47.9	45.6	142.8	132.2
Marine operating revenue	0	0	0	0
Other revenue	2.3	1.9	6.7	5.8
Total Revenues	50.2	47.5	149.5	138.0
Maintenance expense	11.0	10.9	34.1	32.0
Marine operating expense	0	0	0	0
Depreciation	11.9	10.8	35.4	31.5
Operating lease expense	0	0	0	0
Other operating expense	1.2	1.3	3.6	3.6
Total Expenses	24.1	23.0	73.1	67.1
Disposition gains on owned assets	0	0	0.6	0
Residual sharing income	0	0	0	0
Nonremarketing disposition gains	0.9	1.5	5.3	5.3
Asset impairment	(0.1)	(0.2)	(0.1)	(1.5)
Net gain on asset dispositions	0.8	1.3	5.8	3.8
Interest expense, net	(6.0)	(6.7)	(18.4)	(17.5)
Other (expense) income	(1.1)	(1.0)	(3.8)	(0.5)
Share of affiliates' earnings (pre-tax)	(0.1)	16.7	(0.2)	21.1
Segment profit (loss)	19.7	34.8	59.8	77.8
Capital Expenditures
Portfolio investments and capital additions	(45.6)	(43.7)	(127.2)	(134.9)
Selected Balance Sheet Data
Investments in affiliated companies	1.8		1.8		2.0
Identifiable assets	1,234.9		1,234.9		1,297.1
ASC [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity			1.5
Profitability
Lease revenue	1.1	1.1	3.2	3.2
Marine operating revenue	82.7	73.0	145.2	157.0
Other revenue	0	0	0	0
Total Revenues	83.8	74.1	148.4	160.2
Maintenance expense	8.9	7.4	16.4	15.1
Marine operating expense	52.2	47.2	97.9	105.2
Depreciation	4.5	4.1	8.9	8.1
Operating lease expense	1.8	1.8	3.5	3.5
Other operating expense	0	0	0	0
Total Expenses	67.4	60.5	126.7	131.9
Disposition gains on owned assets	0	0	0	0
Residual sharing income	0	0	0	0
Nonremarketing disposition gains	0	0	0	0
Asset impairment	0	0	(0.4)	0
Net gain on asset dispositions	0	0	(0.4)	0
Interest expense, net	(1.4)	(1.6)	(4.2)	(4.8)
Other (expense) income	0.2	0.9	0	0.3
Share of affiliates' earnings (pre-tax)	0	0	0	0
Segment profit (loss)	15.2	12.9	17.1	23.8
Capital Expenditures
Portfolio investments and capital additions	(0.9)	0	(16.9)	(11.0)
Selected Balance Sheet Data
Investments in affiliated companies	0		0		0
Identifiable assets	291.4		291.4		271.0
Portfolio Management [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity			3
Profitability
Lease revenue	7.5	7.8	22.3	24.2
Marine operating revenue	16.2	16.0	43.6	33.8
Other revenue	1.2	1.3	3.7	3.0
Total Revenues	24.9	25.1	69.6	61.0
Maintenance expense	0	0	0	0
Marine operating expense	12.6	11.0	36.5	27.3
Depreciation	5.8	5.8	17.1	17.1
Operating lease expense	0	0	0	0
Other operating expense	0.7	0.7	1.6	1.7
Total Expenses	19.1	17.5	55.2	46.1
Disposition gains on owned assets	0	0.1	0.5	8.4
Residual sharing income	1.1	1.5	3.5	6.6
Nonremarketing disposition gains	0	0	0	0
Asset impairment	0	0.1	0.1	0.1
Net gain on asset dispositions	1.1	1.7	4.1	15.1
Interest expense, net	(5.8)	(6.3)	(18.7)	(19.7)
Other (expense) income	(1.4)	0	(1.1)	0
Share of affiliates' earnings (pre-tax)	17.0	14.7	41.4	37.2
Segment profit (loss)	16.7	17.7	40.1	47.5
Capital Expenditures
Portfolio investments and capital additions	(5.0)	(19.3)	(17.0)	(170.5)
Selected Balance Sheet Data
Investments in affiliated companies	327.9		327.9		320.9
Identifiable assets	816.4		816.4		856.9
Other [Member]
Profitability
Lease revenue	0	0	0	0
Marine operating revenue	0	0	0	0
Other revenue	0	0	0	0
Total Revenues	0	0	0	0
Maintenance expense	0	0	0	0
Marine operating expense	0	0	0	0
Depreciation	0	0	0	0
Operating lease expense	0	0	(0.1)	(0.1)
Other operating expense	0	0	0	0
Total Expenses	0	0	(0.1)	(0.1)
Disposition gains on owned assets	0	0	0	0
Residual sharing income	0	0	0	0
Nonremarketing disposition gains	0	0	0	0
Asset impairment	0	0	0	0
Net gain on asset dispositions	0	0	0	0
Interest expense, net	(0.8)	(0.4)	(4.3)	(2.7)
Other (expense) income	0.2	0.5	(1.8)	0.5
Share of affiliates' earnings (pre-tax)	0	0	0	0
Segment profit (loss)	(0.6)	0.1	(6.0)	(2.1)
Capital Expenditures
Portfolio investments and capital additions	(1.1)	(2.4)	(4.8)	(4.5)
Selected Balance Sheet Data
Investments in affiliated companies	0		0		0
Identifiable assets	142.6		142.6		414.1
Parent [Member]
Profitability
Income tax benefit	$ 24.5	$ 27.6	$ 68.4	$ 57.6