Financial Data of Business Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 Segment	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Provision for Income Taxes, Equity Method Investment									$ 18.3	$ 16.5	$ 2.0
Number of business segments									4
Profitability
Lease revenue									1,086.6	975.2	917.0
Marine operating revenue									286.3	275.1	265.5
Other revenue									78.1	70.7	60.7
Total Revenues	401.4	397.2	365.8	286.6	356.6	353.2	338.9	272.3	1,451.0	1,321.0	1,243.2
Maintenance expense									337.0	294.0	269.7
Marine operating expense									197.8	189.8	182.4
Depreciation									273.5	255.0	237.4
Operating lease expense									108.7	129.4	130.2
Other operating expense									28.9	26.1	24.2
Total Expenses									945.9	894.3	843.9
Net gain on asset dispositions									87.2	85.6	79.5
Interest expense, net									(158.4)	(166.6)	(166.6)
Other (expense) income									(13.5)	(8.4)	(8.2)
Share of affiliates' earnings (pre-tax)									67.8	92.3	21.6
Segment profit (loss)									488.2	429.6	325.6
SG&A									189.2	178.3	160.2
Income tax benefit									75.7	65.5	26.1
Net Income	58.5	51.3	53.1	42.1	53.3	53.8	35.1	27.1	205.0	169.3	137.3
Selected Balance Sheet Data
Investments in affiliated companies	357.7				354.3				357.7	354.3	502.0
Identifiable assets	6,937.5				6,549.6				6,937.5	6,549.6	6,055.4
Capital Expenditures
Portfolio investments and capital additions									(1,030.5)	(859.6)	(770.0)
Rail North America [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									5
Profitability
Lease revenue									864.1	758.9	713.9
Marine operating revenue									0	0	0
Other revenue									63.4	58.2	51.4
Total Revenues									927.5	817.1	765.3
Maintenance expense									265.5	228.2	201.4
Marine operating expense									0	0	0
Depreciation									190.0	176.7	167.7
Operating lease expense									103.7	124.4	126.5
Other operating expense									21.9	18.4	18.5
Total Expenses									581.1	547.7	514.1
Net gain on asset dispositions									72.3	67.7	58.6
Interest expense, net									(98.4)	(106.0)	(101.9)
Other (expense) income									(7.2)	(9.8)	(5.1)
Share of affiliates' earnings (pre-tax)									7.9	10.3	6.5
Segment profit (loss)									321.0	231.6	209.3
Selected Balance Sheet Data
Investments in affiliated companies	17.2				31.4				17.2	31.4	46.9
Identifiable assets	4,358.3				3,710.5				4,358.3	3,710.5	3,601.1
Capital Expenditures
Portfolio investments and capital additions									(810.6)	(502.4)	(465.9)
Rail International [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									2
Profitability
Lease revenue									188.6	180.2	161.2
Marine operating revenue									0	0	0
Other revenue									10.3	8.8	6.5
Total Revenues									198.9	189.0	167.7
Maintenance expense									45.9	42.9	46.6
Marine operating expense									0	0	0
Depreciation									47.1	43.2	36.1
Operating lease expense									0	0	0
Other operating expense									5.1	5.3	5.1
Total Expenses									98.1	91.4	87.8
Net gain on asset dispositions									6.0	3.7	1.7
Interest expense, net									(24.7)	(23.9)	(24.5)
Other (expense) income									(3.1)	(1.1)	(6.1)
Share of affiliates' earnings (pre-tax)									(0.3)	21.1	(18.3)
Segment profit (loss)									78.7	97.4	32.7
Selected Balance Sheet Data
Investments in affiliated companies	1.8				2.0				1.8	2.0	77.2
Identifiable assets	1,229.4				1,297.1				1,229.4	1,297.1	1,105.8
Capital Expenditures
Portfolio investments and capital additions									(163.6)	(168.5)	(200.1)
ASC [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									1.5
Profitability
Lease revenue									4.2	4.2	4.3
Marine operating revenue									223.0	223.5	239.1
Other revenue									0	0	0
Total Revenues									227.2	227.7	243.4
Maintenance expense									25.6	22.9	21.7
Marine operating expense									149.2	151.3	160.3
Depreciation									13.6	12.1	11.9
Operating lease expense									5.2	5.2	3.8
Other operating expense									0	0	(0.3)
Total Expenses									193.6	191.5	197.4
Net gain on asset dispositions									(0.5)	(1.3)	0
Interest expense, net									(5.6)	(6.2)	(7.1)
Other (expense) income									(0.2)	0.2	(1.4)
Share of affiliates' earnings (pre-tax)									0	0	0
Segment profit (loss)									27.3	28.9	37.5
Selected Balance Sheet Data
Investments in affiliated companies	0				0				0	0	0
Identifiable assets	286.7				271.0				286.7	271.0	284.2
Capital Expenditures
Portfolio investments and capital additions									(18.4)	(11.2)	(12.6)
Portfolio Management [Member]
Segment Reporting Information [Line Items]
Leverage level expressed as a ratio of recourse debt to equity									3
Profitability
Lease revenue									29.7	31.9	37.6
Marine operating revenue									63.3	51.6	26.4
Other revenue									4.4	3.7	2.8
Total Revenues									97.4	87.2	66.8
Maintenance expense									0	0	0
Marine operating expense									48.6	38.5	22.1
Depreciation									22.8	23.0	21.7
Operating lease expense									0	0	0.2
Other operating expense									1.9	2.4	0.9
Total Expenses									73.3	63.9	44.9
Net gain on asset dispositions									9.4	15.5	19.2
Interest expense, net									(24.3)	(26.7)	(27.7)
Other (expense) income									(1.2)	1.4	3.4
Share of affiliates' earnings (pre-tax)									60.2	60.9	33.4
Segment profit (loss)									68.2	74.4	50.2
Selected Balance Sheet Data
Investments in affiliated companies	338.7				320.9				338.7	320.9	377.9
Identifiable assets	813.3				856.9				813.3	856.9	797.4
Capital Expenditures
Portfolio investments and capital additions									(32.3)	(170.5)	(83.5)
Other [Member]
Profitability
Lease revenue									0	0	0
Marine operating revenue									0	0	0
Other revenue									0	0	0
Total Revenues									0	0	0
Maintenance expense									0	0	0
Marine operating expense									0	0	0
Depreciation									0	0	0
Operating lease expense									(0.2)	(0.2)	(0.3)
Other operating expense									0	0	0
Total Expenses									(0.2)	(0.2)	(0.3)
Net gain on asset dispositions									0	0	0
Interest expense, net									(5.4)	(3.8)	(5.4)
Other (expense) income									(1.8)	0.9	1.0
Share of affiliates' earnings (pre-tax)									0	0	0
Segment profit (loss)									(7.0)	(2.7)	(4.1)
Selected Balance Sheet Data
Investments in affiliated companies	0				0				0	0	0
Identifiable assets	249.8				414.1				249.8	414.1	266.9
Capital Expenditures
Portfolio investments and capital additions									(5.6)	(7.0)	(7.9)
Parent [Member]
Profitability
Income tax benefit									$ 94.0	$ 82.0	$ 28.1