Financial Data of Business Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 Segment	Mar. 31, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Provision for Income Taxes, Equity Method Investment	$ 4.2	$ 4.1
Number of business segments	4
Profitability
Lease revenue	250.6	237.2
Marine operating revenue	17.7	18.5
Other revenue	18.3	16.6
Total Revenues	286.6	272.3
Maintenance expense	73.1	66.7
Marine operating expense	15.0	16.6
Depreciation	58.7	57.9
Operating lease expense	26.9	32.3
Other operating expense	6.6	5.3
Total Expenses	180.3	178.8
Net gain on asset dispositions	28.1	16.7
Interest expense, net	(42.0)	(40.9)
Other (expense) income	(3.4)	(1.1)
Share of affiliates' earnings (pre-tax)	14.1	12.5
Segment profit (loss)	103.1	80.7
SG&A	42.7	42.0
Income tax benefit	14.1	7.5
Net Income	42.1	27.1
Capital Expenditures
Portfolio investments and capital additions	445.5	149.9
Selected Balance Sheet Data
Investments in affiliated companies	348.5	354.3	354.3
Identifiable assets	7,119.0	6,549.6	6,549.6
Disposition Gains on Owned Assets	21.6	5.8
Nonoperating Income, Residual Sharing Income	1.8	3.9
Nonremarketing Disposition Gain (Loss)	5.0	7.9
Asset Impairment Charges	(0.3)	(0.9)
Rail North America [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity	5
Profitability
Lease revenue	194.9	183.8
Marine operating revenue	0	0
Other revenue	14.6	13.8
Total Revenues	209.5	197.6
Maintenance expense	61.4	54.6
Marine operating expense	0	0
Depreciation	41.5	42.3
Operating lease expense	26.9	32.3
Other operating expense	4.8	4.0
Total Expenses	134.6	133.2
Net gain on asset dispositions	24.8	10.2
Interest expense, net	(24.6)	(25.7)
Other (expense) income	(3.4)	(0.8)
Share of affiliates' earnings (pre-tax)	3.3	2.2
Segment profit (loss)	75.0	50.3
Capital Expenditures
Portfolio investments and capital additions	(396.0)	85.7
Selected Balance Sheet Data
Investments in affiliated companies	21.9	31.4
Identifiable assets	4,186.8	3,710.5
Disposition Gains on Owned Assets	21.6	1.6
Nonoperating Income, Residual Sharing Income	0.6	2.8
Nonremarketing Disposition Gain (Loss)	2.6	6.5
Asset Impairment Charges	0	(0.7)
Rail International [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity	2
Profitability
Lease revenue	47.2	43.0
Marine operating revenue	0	0
Other revenue	2.0	2.2
Total Revenues	49.2	45.2
Maintenance expense	11.5	11.5
Marine operating expense	0	0
Depreciation	11.7	10.1
Operating lease expense	0	0
Other operating expense	1.4	0.9
Total Expenses	24.6	22.5
Net gain on asset dispositions	2.4	1.2
Interest expense, net	(6.2)	(5.6)
Other (expense) income	0	0.5
Share of affiliates' earnings (pre-tax)	(0.1)	(0.2)
Segment profit (loss)	20.7	18.6
Capital Expenditures
Portfolio investments and capital additions	(39.3)	44.3
Selected Balance Sheet Data
Investments in affiliated companies	1.9	2.0
Identifiable assets	1,327.1	1,297.1
Disposition Gains on Owned Assets	0	0
Nonoperating Income, Residual Sharing Income	0	0
Nonremarketing Disposition Gain (Loss)	2.4	1.4
Asset Impairment Charges	0	(0.2)
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
Marine operating revenue	3.1	12.3
Other revenue	0	0
Total Revenues	4.2	13.4
Maintenance expense	0.2	0.6
Marine operating expense	3.4	9.8
Depreciation	0	0
Operating lease expense	0	0
Other operating expense	0	0
Total Expenses	3.6	10.4
Net gain on asset dispositions	(0.4)	0
Interest expense, net	(1.4)	(1.6)
Other (expense) income	0	(0.6)
Share of affiliates' earnings (pre-tax)	0	0
Segment profit (loss)	(1.2)	0.8
Capital Expenditures
Portfolio investments and capital additions	(8.3)	3.2
Selected Balance Sheet Data
Investments in affiliated companies	0	0
Identifiable assets	267.1	271.0
Disposition Gains on Owned Assets	0	0
Nonoperating Income, Residual Sharing Income	0	0
Nonremarketing Disposition Gain (Loss)	0	0
Asset Impairment Charges	(0.4)	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	9.3
Marine operating revenue	14.6	6.2
Other revenue	1.7	0.6
Total Revenues	23.7	16.1
Maintenance expense	0	0
Marine operating expense	11.6	6.8
Depreciation	5.5	5.5
Operating lease expense	0	0
Other operating expense	0.4	0.4
Total Expenses	17.5	12.7
Net gain on asset dispositions	1.3	5.3
Interest expense, net	(6.8)	(6.7)
Other (expense) income	0.3	0
Share of affiliates' earnings (pre-tax)	10.9	10.5
Segment profit (loss)	11.9	12.5
Capital Expenditures
Portfolio investments and capital additions	0	16.0
Selected Balance Sheet Data
Investments in affiliated companies	324.7	320.9
Identifiable assets	854.6	856.9
Disposition Gains on Owned Assets	0	4.2
Nonoperating Income, Residual Sharing Income	1.2	1.1
Nonremarketing Disposition Gain (Loss)	0	0
Asset Impairment Charges	0.1	0
Other [Member]
Profitability
Lease revenue	0	0
Marine operating revenue	0	0
Other revenue	0	0
Total Revenues	0	0
Maintenance expense	0	0
Marine operating expense	0	0
Depreciation	0	0
Operating lease expense	0	0
Other operating expense	0	0
Total Expenses	0	0
Net gain on asset dispositions	0	0
Interest expense, net	(3.0)	(1.3)
Other (expense) income	(0.3)	(0.2)
Share of affiliates' earnings (pre-tax)	0	0
Segment profit (loss)	(3.3)	(1.5)
Capital Expenditures
Portfolio investments and capital additions	(1.9)	0.7
Selected Balance Sheet Data
Investments in affiliated companies	0	0
Identifiable assets	483.4	414.1
Disposition Gains on Owned Assets	0	0
Nonoperating Income, Residual Sharing Income	0	0
Nonremarketing Disposition Gain (Loss)	0	0
Asset Impairment Charges	0	0
Parent [Member]
Profitability
Income tax benefit	$ 18.3	$ 11.6