Financial Data of Business Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Segment	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Provision for Income Taxes, Equity Method Investment	$ 5.4	$ 9.3	$ 9.6	$ 13.4
Number of business segments			4
Profitability
Lease revenue	274.3	239.0	524.9	476.2
Marine operating revenue	72.2	83.3	89.9	101.8
Other revenue	19.3	16.6	37.6	33.2
Total Revenues	365.8	338.9	652.4	611.2
Maintenance expense	84.0	74.3	157.1	141.0
Marine operating expense	54.6	57.7	69.6	74.3
Depreciation	71.1	63.1	129.8	121.0
Operating lease expense	27.3	33.6	54.2	65.9
Other operating expense	6.7	7.0	13.3	12.3
Total Expenses	243.7	235.7	424.0	414.5
Disposition gains on owned assets	18.8	11.4	40.4	17.2
Residual sharing income	5.0	4.1	6.8	8.0
Nonremarketing disposition gains	4.4	5.2	9.4	13.1
Asset impairment	0	(1.1)	(0.3)	(2.0)
Net gain on asset dispositions	28.2	19.6	56.3	36.3
Interest expense, net	(39.5)	(43.2)	(81.5)	(84.1)
Other (expense) income	(4.9)	(3.1)	(8.3)	(4.2)
Share of affiliates' earnings (pre-tax)	17.7	22.8	31.8	35.3
Segment profit (loss)	123.6	99.3	226.7	180.0
SG&A	44.9	45.8	87.6	87.8
Income tax benefit	20.2	9.1	34.3	16.6
Net Income	53.1	35.1	95.2	62.2
Capital Expenditures
Portfolio investments and capital additions	209.6	320.7	655.1	470.6
Selected Balance Sheet Data
Investments in affiliated companies	356.7		356.7		354.3
Identifiable assets	6,921.1		6,921.1		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	218.2	187.3	413.1	371.1
Marine operating revenue	0	0	0	0
Other revenue	16.1	13.8	30.7	27.6
Total Revenues	234.3	201.1	443.8	398.7
Maintenance expense	65.1	57.6	126.5	112.2
Marine operating expense	0	0	0	0
Depreciation	49.1	42.7	90.6	85.0
Operating lease expense	25.7	32.0	52.6	64.3
Other operating expense	5.2	5.0	10.0	9.0
Total Expenses	145.1	137.3	279.7	270.5
Disposition gains on owned assets	17.7	7.3	39.3	8.9
Residual sharing income	3.8	0.1	4.4	2.9
Nonremarketing disposition gains	2.4	2.8	5.0	9.3
Asset impairment	0	0	0	(0.7)
Net gain on asset dispositions	23.9	10.2	48.7	20.4
Interest expense, net	(25.3)	(28.7)	(49.9)	(54.4)
Other (expense) income	(0.3)	(3.3)	(3.7)	(4.1)
Share of affiliates' earnings (pre-tax)	4.2	6.2	7.5	8.4
Segment profit (loss)	91.7	48.2	166.7	98.5
Capital Expenditures
Portfolio investments and capital additions	(145.8)	(129.4)	(541.8)	(215.1)
Selected Balance Sheet Data
Investments in affiliated companies	18.5		18.5		31.4
Identifiable assets	4,273.4		4,273.4		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	47.7	43.6	94.9	86.6
Marine operating revenue	0	0	0	0
Other revenue	2.4	1.7	4.4	3.9
Total Revenues	50.1	45.3	99.3	90.5
Maintenance expense	11.6	9.6	23.1	21.1
Marine operating expense	0	0	0	0
Depreciation	11.8	10.6	23.5	20.7
Operating lease expense	0	0	0	0
Other operating expense	1.0	1.4	2.4	2.3
Total Expenses	24.4	21.6	49.0	44.1
Disposition gains on owned assets	0.6	0	0.6	0
Residual sharing income	0	0	0	0
Nonremarketing disposition gains	2.0	2.4	4.4	3.8
Asset impairment	0	(1.1)	0	(1.3)
Net gain on asset dispositions	2.6	1.3	5.0	2.5
Interest expense, net	(6.2)	(5.2)	(12.4)	(10.8)
Other (expense) income	(2.7)	0	(2.7)	0.5
Share of affiliates' earnings (pre-tax)	0	4.6	(0.1)	4.4
Segment profit (loss)	19.4	24.4	40.1	43.0
Capital Expenditures
Portfolio investments and capital additions	(42.3)	(46.9)	(81.6)	(91.2)
Selected Balance Sheet Data
Investments in affiliated companies	1.9		1.9		2.0
Identifiable assets	1,349.1		1,349.1		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	1.0	1.0	2.1	2.1
Marine operating revenue	59.4	71.7	62.5	84.0
Other revenue	0	0	0	0
Total Revenues	60.4	72.7	64.6	86.1
Maintenance expense	7.3	7.1	7.5	7.7
Marine operating expense	42.3	48.2	45.7	58.0
Depreciation	4.4	4.0	4.4	4.0
Operating lease expense	1.7	1.7	1.7	1.7
Other operating expense	0	0	0	0
Total Expenses	55.7	61.0	59.3	71.4
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)	(2.8)	(3.2)
Other (expense) income	(0.2)	0	(0.2)	(0.6)
Share of affiliates' earnings (pre-tax)	0	0	0	0
Segment profit (loss)	3.1	10.1	1.9	10.9
Capital Expenditures
Portfolio investments and capital additions	(7.7)	(7.8)	(16.0)	(11.0)
Selected Balance Sheet Data
Investments in affiliated companies	0		0		0
Identifiable assets	300.6		300.6		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	7.4	7.1	14.8	16.4
Marine operating revenue	12.8	11.6	27.4	17.8
Other revenue	0.8	1.1	2.5	1.7
Total Revenues	21.0	19.8	44.7	35.9
Maintenance expense	0	0	0	0
Marine operating expense	12.3	9.5	23.9	16.3
Depreciation	5.8	5.8	11.3	11.3
Operating lease expense	0	0	0	0
Other operating expense	0.5	0.6	0.9	1.0
Total Expenses	18.6	15.9	36.1	28.6
Disposition gains on owned assets	0.5	4.1	0.5	8.3
Residual sharing income	1.2	4.0	2.4	5.1
Nonremarketing disposition gains	0	0	0	0
Asset impairment	0	0	0.1	0
Net gain on asset dispositions	1.7	8.1	3.0	13.4
Interest expense, net	(6.1)	(6.7)	(12.9)	(13.4)
Other (expense) income	0	0	0.3	0
Share of affiliates' earnings (pre-tax)	13.5	12.0	24.4	22.5
Segment profit (loss)	11.5	17.3	23.4	29.8
Capital Expenditures
Portfolio investments and capital additions	(12.0)	(135.2)	(12.0)	(151.2)
Selected Balance Sheet Data
Investments in affiliated companies	336.3		336.3		320.9
Identifiable assets	859.3		859.3		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	(0.1)	(0.1)	(0.1)	(0.1)
Other operating expense	0	0	0	0
Total Expenses	(0.1)	(0.1)	(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	(0.5)	(1.0)	(3.5)	(2.3)
Other (expense) income	(1.7)	0.2	(2.0)	0
Share of affiliates' earnings (pre-tax)	0	0	0	0
Segment profit (loss)	(2.1)	(0.7)	(5.4)	(2.2)
Capital Expenditures
Portfolio investments and capital additions	(1.8)	(1.4)	(3.7)	(2.1)
Selected Balance Sheet Data
Investments in affiliated companies	0		0		0
Identifiable assets	138.7		138.7		414.1
Parent [Member]
Profitability
Income tax benefit	$ 25.6	$ 18.4	$ 43.9	$ 30.0