Financial Data of Business Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 Segment	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Lease Income	$ 278.3	$ 250.6
Cargo and Freight Revenue	24.2	17.7
Provision for Income Taxes, Equity Method Investment	3.0	4.2
Number of business segments	4
Profitability
Other revenue	17.2	18.3
Maintenance expense	78.3	73.1
Depreciation expense	68.5	58.7
Marine operating expense	18.9	15.0
Operating lease expense	20.7	26.9
Other operating expense	7.3	6.6
Total Expenses	193.7	180.3
Disposition gains on owned assets	37.9	21.6
Residual sharing income	1.8	1.8
Nonremarketing disposition gains	5.7	5.0
Asset impairment	(0.1)	(0.3)
Net gain on asset dispositions	45.3	28.1
Interest expense, net	(40.9)	(42.0)
Other (expense) income	(4.0)	(3.4)
Share of affiliates' earnings (pre-tax)	11.5	14.1
Segment profit (loss)	137.9	103.1
SG&A	45.7	42.7
Income tax benefit	27.0	14.1
Net Income	62.2	42.1
Revenues	319.7	286.6
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	180.9	445.5
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	359.7		357.7
Identifiable assets	7,056.4		6,937.5
Rail North America [Member]
Segment Reporting Information [Line Items]
Lease Income	228.5	194.9
Cargo and Freight Revenue	0	0
Leverage level expressed as a ratio of recourse debt to equity	5
Profitability
Other revenue	14.7	14.6
Maintenance expense	69.2	61.4
Depreciation expense	52.3	41.5
Marine operating expense	0	0
Operating lease expense	20.7	26.9
Other operating expense	5.5	4.8
Total Expenses	147.7	134.6
Disposition gains on owned assets	35.9	21.6
Residual sharing income	0.2	0.6
Nonremarketing disposition gains	0.7	2.6
Asset impairment	0	0
Net gain on asset dispositions	36.8	24.8
Interest expense, net	(24.5)	(24.6)
Other (expense) income	(2.2)	(3.4)
Share of affiliates' earnings (pre-tax)	0.2	3.3
Segment profit (loss)	105.8	75.0
Revenues	243.2	209.5
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	129.8	396.0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	13.9		17.2
Identifiable assets	4,518.9		4,358.3
Rail International [Member]
Segment Reporting Information [Line Items]
Lease Income	42.1	47.2
Cargo and Freight Revenue	0	0
Leverage level expressed as a ratio of recourse debt to equity	2
Profitability
Other revenue	1.9	2.0
Maintenance expense	8.9	11.5
Depreciation expense	10.7	11.7
Marine operating expense	0	0
Operating lease expense	0	0
Other operating expense	0.9	1.4
Total Expenses	20.5	24.6
Disposition gains on owned assets	0	0
Residual sharing income	0	0
Nonremarketing disposition gains	5.0	2.4
Asset impairment	(0.1)	0
Net gain on asset dispositions	4.9	2.4
Interest expense, net	(6.5)	(6.2)
Other (expense) income	0	0
Share of affiliates' earnings (pre-tax)	(0.1)	(0.1)
Segment profit (loss)	21.8	20.7
Revenues	44.0	49.2
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	41.4	39.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	1.6		1.8
Identifiable assets	1,161.0		1,229.4
ASC [Member]
Segment Reporting Information [Line Items]
Lease Income	1.0	1.1
Cargo and Freight Revenue	7.0	3.1
Leverage level expressed as a ratio of recourse debt to equity	1.5
Profitability
Other revenue	0	0
Maintenance expense	0.2	0.2
Depreciation expense	0	0
Marine operating expense	6.9	3.4
Operating lease expense	0	0
Other operating expense	0	0
Total Expenses	7.1	3.6
Disposition gains on owned assets	0	0
Residual sharing income	0	0
Nonremarketing disposition gains	0	0
Asset impairment	0	(0.4)
Net gain on asset dispositions	0	(0.4)
Interest expense, net	(1.3)	(1.4)
Other (expense) income	0	0
Share of affiliates' earnings (pre-tax)	0	0
Segment profit (loss)	(0.4)	(1.2)
Revenues	8.0	4.2
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	9.3	8.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0		0
Identifiable assets	273.5		286.7
Portfolio Management [Member]
Segment Reporting Information [Line Items]
Lease Income	6.7	7.4
Cargo and Freight Revenue	17.2	14.6
Leverage level expressed as a ratio of recourse debt to equity	3
Profitability
Other revenue	0.6	1.7
Maintenance expense	0	0
Depreciation expense	5.5	5.5
Marine operating expense	12.0	11.6
Operating lease expense	0	0
Other operating expense	0.9	0.4
Total Expenses	18.4	17.5
Disposition gains on owned assets	2.0	0
Residual sharing income	1.6	1.2
Nonremarketing disposition gains	0	0
Asset impairment	0	0.1
Net gain on asset dispositions	3.6	1.3
Interest expense, net	(5.2)	(6.8)
Other (expense) income	0	0.3
Share of affiliates' earnings (pre-tax)	11.4	10.9
Segment profit (loss)	15.9	11.9
Revenues	24.5	23.7
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	344.2		338.7
Identifiable assets	794.4		813.3
Other [Member]
Segment Reporting Information [Line Items]
Lease Income	0	0
Cargo and Freight Revenue	0	0
Profitability
Other revenue	0	0
Maintenance expense	0	0
Depreciation expense	0	0
Marine operating expense	0	0
Operating lease expense	0	0
Other operating expense	0	0
Total Expenses	0	0
Disposition gains on owned assets	0	0
Residual sharing income	0	0
Nonremarketing disposition gains	0	0
Asset impairment	0	0
Net gain on asset dispositions	0	0
Interest expense, net	(3.4)	(3.0)
Other (expense) income	(1.8)	(0.3)
Share of affiliates' earnings (pre-tax)	0	0
Segment profit (loss)	(5.2)	(3.3)
Revenues	0	0
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	0.4	1.9
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0		0
Identifiable assets	308.6		249.8
Parent [Member]
Profitability
Income tax benefit	$ 30.0	$ 18.3