Financial Data of Business Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013 affiliate_investment	Mar. 31, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Number of business segments	4
Income taxes related to affiliates' earnings	$ 4.1	$ 2.4
Profitability
Lease revenue	237.2	225.5
Marine operating revenue	18.5	17.5
Other revenue	16.6	13.5
Total Revenues	272.3	256.5
Maintenance expense	66.7	60.9
Marine operating expense	16.6	13.5
Depreciation	57.9	55.7
Operating lease expense	32.3	31.4
Other operating expense	5.3	3.7
Total Expenses	178.8	165.2
Net gain on asset dispositions	16.7	28.0
Interest expense, net	(40.9)	(42.6)
Other (expense) income	(1.1)	(0.6)
Share of affiliates' earnings (pre-tax)	12.5	5.5
Segment profit (loss)	80.7	81.6
Selling, general and administrative expense	42.0	38.1
Income taxes, including tax related to affiliates' earnings	11.6	13.2
Net Income	27.1	30.3
Capital Expenditures
Portfolio investments and capital additions	149.9	153.7
Selected Balance Sheet Data
Investments in affiliated companies	485.5	502.0	502.0
Identifiable assets	6,144.7	6,055.4	6,055.4
Rail North America [Member]
Segment Reporting Information [Line Items]
Number of affiliate investments	2
Leverage level expressed as a ratio of recourse debt to equity			5.0
Profitability
Lease revenue	183.8	174.6
Marine operating revenue	0	0
Other revenue	13.8	11.8
Total Revenues	197.6	186.4
Maintenance expense	54.6	48.0
Marine operating expense	0	0
Depreciation	42.3	41.7
Operating lease expense	32.3	31.4
Other operating expense	4.0	4.4
Total Expenses	133.2	125.5
Net gain on asset dispositions	10.2	16.0
Interest expense, net	(25.7)	(25.8)
Other (expense) income	(0.8)	(1.9)
Share of affiliates' earnings (pre-tax)	2.2	1.5
Segment profit (loss)	50.3	50.7
Capital Expenditures
Portfolio investments and capital additions	85.7	98.9
Selected Balance Sheet Data
Investments in affiliated companies	47.0	46.9
Identifiable assets	3,639.6	3,601.1
Rail International [Member]
Segment Reporting Information [Line Items]
Number of affiliate investments	2
Leverage level expressed as a ratio of recourse debt to equity			2.0
Profitability
Lease revenue	43.0	40.0
Marine operating revenue	0	0
Other revenue	2.2	0.9
Total Revenues	45.2	40.9
Maintenance expense	11.5	12.5
Marine operating expense	0	0
Depreciation	10.1	8.6
Operating lease expense	0	0
Other operating expense	0.9	1.1
Total Expenses	22.5	22.2
Net gain on asset dispositions	1.2	0.9
Interest expense, net	(5.6)	(6.4)
Other (expense) income	0.5	(1.8)
Share of affiliates' earnings (pre-tax)	(0.2)	(3.5)
Segment profit (loss)	18.6	7.9
Capital Expenditures
Portfolio investments and capital additions	44.3	44.8
Selected Balance Sheet Data
Investments in affiliated companies	79.8	77.2
Identifiable assets	1,111.4	1,105.8
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	12.3	10.7
Other revenue	0	0
Total Revenues	13.4	11.8
Maintenance expense	0.6	0.4
Marine operating expense	9.8	7.7
Depreciation	0	0
Operating lease expense	0	0
Other operating expense	0	(0.2)
Total Expenses	10.4	7.9
Net gain on asset dispositions	0	0
Interest expense, net	(1.6)	(1.8)
Other (expense) income	(0.6)	0
Share of affiliates' earnings (pre-tax)	0	0
Segment profit (loss)	0.8	2.1
Capital Expenditures
Portfolio investments and capital additions	3.2	5.9
Selected Balance Sheet Data
Investments in affiliated companies	0	0
Identifiable assets	271.8	284.2
Portfolio Management [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity			3.0
Profitability
Lease revenue	9.3	9.8
Marine operating revenue	6.2	6.8
Other revenue	0.6	0.8
Total Revenues	16.1	17.4
Maintenance expense	0	0
Marine operating expense	6.8	5.8
Depreciation	5.5	5.4
Operating lease expense	0	0.1
Other operating expense	0.4	(1.6)
Total Expenses	12.7	9.7
Net gain on asset dispositions	5.3	11.1
Interest expense, net	(6.7)	(7.2)
Other (expense) income	0	2.9
Share of affiliates' earnings (pre-tax)	10.5	7.5
Segment profit (loss)	12.5	22.0
Capital Expenditures
Portfolio investments and capital additions	16.0	3.1
Selected Balance Sheet Data
Investments in affiliated companies	358.7	377.9
Identifiable assets	766.3	797.4
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	(0.1)
Other operating expense	0	0
Total Expenses	0	(0.1)
Net gain on asset dispositions	0	0
Interest expense, net	(1.3)	(1.4)
Other (expense) income	(0.2)	0.2
Share of affiliates' earnings (pre-tax)	0	0
Segment profit (loss)	(1.5)	(1.1)
Capital Expenditures
Portfolio investments and capital additions	0.7	1.0
Selected Balance Sheet Data
Investments in affiliated companies	0	0
Identifiable assets	$ 355.6	$ 266.9