Financial Data of Business Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		9 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Segment	Jun. 30, 2012	Sep. 30, 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	239.0	225.6	476.2	451.1
Marine operating revenue	83.3	83.1	101.8	100.6
Other Revenue, Net	16.6	14.4	33.2	27.9
Total Revenues	338.9	323.1	611.2	579.6
Maintenance expense	74.3	67.8	141.0	128.7
Marine operating expense	57.7	55.2	74.3	68.7
Depreciation	63.1	59.5	121.0	115.2
Operating lease expense	33.6	32.5	65.9	63.9
Other operating expense	7.0	6.3	12.3	10.0
Total Expenses	235.7	221.3	414.5	386.5
Net gain on asset dispositions	19.6	18.3	36.3	46.3
Interest expense, net	(43.2)	(41.6)	(84.1)	(84.2)
Other (expense) income	(3.1)	0.5	(4.2)	(0.1)
Share of affiliates' earnings (pre-tax)	22.8	(1.3)	35.3	4.2
Segment profit (loss)	99.3	77.7	180.0	159.3
Selling, general and administrative expense	45.8	38.9	87.8	77.0
Income taxes, including tax related to affiliates' earnings	18.4	15.3	30.0	28.5
Net Income	35.1	23.5	62.2	53.8	62.2
Capital Expenditures
Portfolio investments and capital additions	320.7	238.1	470.6	391.8
Selected Balance Sheet Data
Investments in affiliated companies	424.3	502.0	424.3	502.0		502.0
Identifiable assets	6,119.2	6,055.4	6,119.2	6,055.4		6,055.4
Rail North America [Member]
Segment Reporting Information [Line Items]
Number of affiliate investments	2		2
Leverage level expressed as a ratio of recourse debt to equity			5.0
Profitability
Lease revenue	187.3	176.6	371.1	351.2
Marine operating revenue	0	0	0	0
Other Revenue, Net	13.8	12.1	27.6	23.9
Total Revenues	201.1	188.7	398.7	375.1
Maintenance expense	57.6	48.8	112.2	96.8
Marine operating expense	0	0	0	0
Depreciation	42.7	41.8	85.0	83.5
Operating lease expense	32.0	31.3	64.3	62.7
Other operating expense	5.0	4.0	9.0	8.4
Total Expenses	137.3	125.9	270.5	251.4
Net gain on asset dispositions	10.2	14.5	20.4	30.5
Interest expense, net	(28.7)	(25.9)	(54.4)	(51.7)
Other (expense) income	(3.3)	(0.2)	(4.1)	(2.1)
Share of affiliates' earnings (pre-tax)	6.2	2.0	8.4	3.5
Segment profit (loss)	48.2	53.2	98.5	103.9
Capital Expenditures
Portfolio investments and capital additions	(129.4)	(137.7)	(215.1)	(236.6)
Selected Balance Sheet Data
Investments in affiliated companies	33.5	46.9	33.5	46.9
Identifiable assets	3,710.2	3,601.1	3,710.2	3,601.1
Rail International [Member]
Segment Reporting Information [Line Items]
Number of affiliate investments	2		2
Leverage level expressed as a ratio of recourse debt to equity			2.0
Profitability
Lease revenue	43.6	39.0	86.6	79.0
Marine operating revenue	0	0	0	0
Other Revenue, Net	1.7	1.6	3.9	2.5
Total Revenues	45.3	40.6	90.5	81.5
Maintenance expense	9.6	12.3	21.1	24.8
Marine operating expense	0	0	0	0
Depreciation	10.6	8.6	20.7	17.2
Operating lease expense	0	0	0	0
Other operating expense	1.4	1.8	2.3	2.9
Total Expenses	21.6	22.7	44.1	44.9
Net gain on asset dispositions	1.3	1.2	2.5	2.1
Interest expense, net	(5.2)	(6.5)	(10.8)	(12.9)
Other (expense) income	0	0.3	0.5	(1.5)
Share of affiliates' earnings (pre-tax)	4.6	(16.5)	4.4	(20.0)
Segment profit (loss)	24.4	(3.6)	43.0	4.3
Capital Expenditures
Portfolio investments and capital additions	(46.9)	(39.2)	(91.2)	(84.0)
Selected Balance Sheet Data
Investments in affiliated companies	83.8	77.2	83.8	77.2
Identifiable assets	1,151.1	1,105.8	1,151.1	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	1.0	1.0	2.1	2.1
Marine operating revenue	71.7	76.2	84.0	86.9
Other Revenue, Net	0	0	0	0
Total Revenues	72.7	77.2	86.1	89.0
Maintenance expense	7.1	6.7	7.7	7.1
Marine operating expense	48.2	49.6	58.0	57.3
Depreciation	4.0	3.9	4.0	3.9
Operating lease expense	1.7	1.2	1.7	1.2
Other operating expense	0	(0.1)	0	(0.3)
Total Expenses	61.0	61.3	71.4	69.2
Net gain on asset dispositions	0	0	0	0
Interest expense, net	(1.6)	(1.9)	(3.2)	(3.7)
Other (expense) income	0	0	(0.6)	0
Share of affiliates' earnings (pre-tax)	0	0	0	0
Segment profit (loss)	10.1	14.0	10.9	16.1
Capital Expenditures
Portfolio investments and capital additions	(7.8)	(5.5)	(11.0)	(11.4)
Selected Balance Sheet Data
Investments in affiliated companies	0	0	0	0
Identifiable assets	298.6	284.2	298.6	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	7.1	9.0	16.4	18.8
Marine operating revenue	11.6	6.9	17.8	13.7
Other Revenue, Net	1.1	0.7	1.7	1.5
Total Revenues	19.8	16.6	35.9	34.0
Maintenance expense	0	0	0	0
Marine operating expense	9.5	5.6	16.3	11.4
Depreciation	5.8	5.2	11.3	10.6
Operating lease expense	0	0.1	0	0.2
Other operating expense	0.6	0.6	1.0	(1.0)
Total Expenses	15.9	11.5	28.6	21.2
Net gain on asset dispositions	8.1	2.6	13.4	13.7
Interest expense, net	(6.7)	(6.5)	(13.4)	(13.7)
Other (expense) income	0	0.2	0	3.1
Share of affiliates' earnings (pre-tax)	12.0	13.2	22.5	20.7
Segment profit (loss)	17.3	14.6	29.8	36.6
Capital Expenditures
Portfolio investments and capital additions	(135.2)	(53.4)	(151.2)	(56.5)
Selected Balance Sheet Data
Investments in affiliated companies	307.0	377.9	307.0	377.9
Identifiable assets	828.0	797.4	828.0	797.4
Other [Member]
Profitability
Lease revenue	0	0	0	0
Marine operating revenue	0	0	0	0
Other Revenue, Net	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)	(0.2)
Other operating expense	0	0	0	0
Total Expenses	(0.1)	(0.1)	(0.1)	(0.2)
Net gain on asset dispositions	0	0	0	0
Interest expense, net	(1.0)	(0.8)	(2.3)	(2.2)
Other (expense) income	0.2	0.2	0	0.4
Share of affiliates' earnings (pre-tax)	0	0	0	0
Segment profit (loss)	(0.7)	(0.5)	(2.2)	(1.6)
Capital Expenditures
Portfolio investments and capital additions	(1.4)	(2.3)	(2.1)	(3.3)
Selected Balance Sheet Data
Investments in affiliated companies	0	0	0	0
Identifiable assets	$ 131.3	$ 266.9	$ 131.3	$ 266.9