Financial Data of Business Segments (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) Segment	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Lease Income	$ 281.2	$ 280.6	$ 565.7	$ 558.9
Cargo and Freight Revenue	57.3	66.0	77.6	90.2
Provision for Income Taxes, Equity Method Investment	1.4	3.0	$ 4.1	6.0
Number of business segments | Segment			4
Profitability
Other revenue	20.4	18.7	$ 50.0	35.9
Maintenance expense	86.5	80.2	165.0	158.5
Depreciation expense	75.8	74.4	145.1	142.9
Marine operating expense	37.4	47.3	49.7	66.2
Operating lease expense	18.5	22.4	35.3	43.1
Other operating expense	14.8	7.8	23.6	15.1
Total Expenses	233.0	232.1	418.7	425.8
Disposition gains on owned assets	5.1	5.1	25.1	43.0
Residual sharing income	31.7	1.6	33.5	3.4
Nonremarketing disposition gains	1.9	2.0	3.3	7.7
Asset impairment	(1.8)	0.0	(1.8)	(0.1)
Net gain on asset dispositions	36.9	8.7	60.1	54.0
Interest Revenue (Expense), Net	(36.5)	(38.5)	(73.7)	(79.4)
Other (expense) income	(3.9)	(1.6)	(7.2)	(5.6)
Income (Loss) From Equity Method Investment, Before Tax	7.8	12.0	18.0	23.5
Segment profit (loss)	130.2	113.8	271.8	251.7
SG&A	40.9	44.6	79.7	90.3
Income tax benefit	26.7	20.8	57.5	47.8
Net Income	61.2	45.4	130.5	107.6
Revenues	358.9	365.3	693.3	685.0
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	182.0	175.3	322.2	356.2
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	361.1		361.1		$ 348.5
Identifiable assets	7,090.6		7,090.6		6,894.2
Rail North America [Member]
Segment Reporting Information [Line Items]
Lease Income	233.4	230.9	470.0	459.4
Cargo and Freight Revenue	0.0	0.0	$ 0.0	0.0
Leverage level expressed as a ratio of recourse debt to equity			5
Profitability
Other revenue	18.4	16.8	$ 46.2	31.5
Maintenance expense	67.6	63.8	133.4	133.0
Depreciation expense	58.1	53.3	114.6	105.6
Marine operating expense	0.0	0.0	0.0	0.0
Operating lease expense	16.6	20.7	33.4	41.4
Other operating expense	9.5	5.8	16.4	11.3
Total Expenses	151.8	143.6	297.8	291.3
Disposition gains on owned assets	3.0	5.0	20.6	40.9
Residual sharing income	0.1	0.2	0.4	0.4
Nonremarketing disposition gains	1.6	0.9	2.3	1.6
Asset impairment	0.0	0.0	0.0	0.0
Net gain on asset dispositions	4.7	6.1	23.3	42.9
Interest Revenue (Expense), Net	(26.9)	(24.6)	(54.1)	(49.1)
Other (expense) income	(1.1)	(0.8)	(2.4)	(3.0)
Income (Loss) From Equity Method Investment, Before Tax	0.1	0.1	0.3	0.3
Segment profit (loss)	76.8	84.9	185.5	190.7
Revenues	251.8	247.7	516.2	490.9
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	145.4	135.2	258.3	265.0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	10.9		10.9		12.0
Identifiable assets	4,820.6		4,820.6		4,629.1
Rail International [Member]
Segment Reporting Information [Line Items]
Lease Income	45.3	42.4	90.2	84.5
Cargo and Freight Revenue	0.0	0.0	$ 0.0	0.0
Leverage level expressed as a ratio of recourse debt to equity			2
Profitability
Other revenue	1.6	1.7	$ 3.2	3.6
Maintenance expense	12.9	9.4	25.4	18.3
Depreciation expense	11.5	10.8	22.6	21.5
Marine operating expense	0.0	0.0	0.0	0.0
Operating lease expense	0.0	0.1	0.0	0.1
Other operating expense	1.2	1.5	2.6	2.4
Total Expenses	25.6	21.8	50.6	42.3
Disposition gains on owned assets	0.0	0.0	0.0	0.0
Residual sharing income	0.0	0.0	0.0	0.0
Nonremarketing disposition gains	0.3	1.1	1.0	6.1
Asset impairment	0.0	0.0	0.0	(0.1)
Net gain on asset dispositions	0.3	1.1	1.0	6.0
Interest Revenue (Expense), Net	(7.3)	(3.0)	(14.6)	(9.5)
Other (expense) income	(1.3)	(1.2)	(3.5)	(1.2)
Income (Loss) From Equity Method Investment, Before Tax	0.0	(0.1)	(0.1)	(0.2)
Segment profit (loss)	13.0	19.1	25.6	40.9
Revenues	46.9	44.1	93.4	88.1
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	30.4	27.8	52.4	69.2
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	1.3		1.3		1.4
Identifiable assets	1,172.7		1,172.7		1,117.6
ASC [Member]
Segment Reporting Information [Line Items]
Lease Income	1.1	1.0	2.1	2.0
Cargo and Freight Revenue	46.4	51.0	$ 50.5	58.0
Leverage level expressed as a ratio of recourse debt to equity			1.5
Profitability
Other revenue	0.0	0.0	$ 0.0	0.0
Maintenance expense	6.0	7.0	6.2	7.2
Depreciation expense	4.4	4.9	4.4	4.9
Marine operating expense	29.6	34.1	32.5	41.0
Operating lease expense	2.0	1.7	2.0	1.7
Other operating expense	0.0	0.0	0.0	0.0
Total Expenses	42.0	47.7	45.1	54.8
Disposition gains on owned assets	0.0	0.0	0.0	0.0
Residual sharing income	0.0	0.0	0.0	0.0
Nonremarketing disposition gains	0.0	0.0	0.0	0.0
Asset impairment	0.0	0.0	0.0	0.0
Net gain on asset dispositions	0.0	0.0	0.0	0.0
Interest Revenue (Expense), Net	(1.1)	(1.3)	(2.2)	(2.6)
Other (expense) income	(0.2)	(0.1)	(0.2)	(0.1)
Income (Loss) From Equity Method Investment, Before Tax	0.0	0.0	0.0	0.0
Segment profit (loss)	4.2	2.9	5.1	2.5
Revenues	47.5	52.0	52.6	60.0
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	4.4	10.2	9.1	19.5
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0.0		0.0		0.0
Identifiable assets	296.3		296.3		284.7
Portfolio Management [Member]
Segment Reporting Information [Line Items]
Lease Income	1.4	6.3	3.4	13.0
Cargo and Freight Revenue	10.9	15.0	$ 27.1	32.2
Leverage level expressed as a ratio of recourse debt to equity			3
Profitability
Other revenue	0.4	0.2	$ 0.6	0.8
Maintenance expense	0.0	0.0	0.0	0.0
Depreciation expense	1.8	5.4	3.5	10.9
Marine operating expense	7.8	13.2	17.2	25.2
Operating lease expense	0.0	0.0	0.0	0.0
Other operating expense	4.1	0.5	4.6	1.4
Total Expenses	13.7	19.1	25.3	37.5
Disposition gains on owned assets	2.1	0.1	4.5	2.1
Residual sharing income	31.6	1.4	33.1	3.0
Nonremarketing disposition gains	0.0	0.0	0.0	0.0
Asset impairment	(1.8)	0.0	(1.8)	0.0
Net gain on asset dispositions	31.9	1.5	35.8	5.1
Interest Revenue (Expense), Net	(2.1)	(5.6)	(4.3)	(10.8)
Other (expense) income	0.0	0.0	0.0	0.0
Income (Loss) From Equity Method Investment, Before Tax	7.7	12.0	17.8	23.4
Segment profit (loss)	36.5	10.3	55.1	26.2
Revenues	12.7	21.5	31.1	46.0
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	0.0	0.3	0.0	0.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	348.9		348.9		335.1
Identifiable assets	617.0		617.0		636.5
Other [Member]
Segment Reporting Information [Line Items]
Lease Income	0.0	0.0	0.0	0.0
Cargo and Freight Revenue	0.0	0.0	0.0	0.0
Profitability
Other revenue	0.0	0.0	0.0	0.0
Maintenance expense	0.0	0.0	0.0	0.0
Depreciation expense	0.0	0.0	0.0	0.0
Marine operating expense	0.0	0.0	0.0	0.0
Operating lease expense	(0.1)	(0.1)	(0.1)	(0.1)
Other operating expense	0.0	0.0	0.0	0.0
Total Expenses	(0.1)	(0.1)	(0.1)	(0.1)
Disposition gains on owned assets	0.0	0.0	0.0	0.0
Residual sharing income	0.0	0.0	0.0	0.0
Nonremarketing disposition gains	0.0	0.0	0.0	0.0
Asset impairment	0.0	0.0	0.0	0.0
Net gain on asset dispositions	0.0	0.0	0.0	0.0
Interest Revenue (Expense), Net	0.9	(4.0)	1.5	(7.4)
Other (expense) income	(1.3)	0.5	(1.1)	(1.3)
Income (Loss) From Equity Method Investment, Before Tax	0.0	0.0	0.0	0.0
Segment profit (loss)	(0.3)	(3.4)	0.5	(8.6)
Revenues	0.0	0.0	0.0	0.0
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	1.8	1.8	2.4	2.2
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0.0		0.0		0.0
Identifiable assets	184.0		184.0		$ 226.3
Parent [Member]
Profitability
Income tax benefit	$ 28.1	$ 23.8	$ 61.6	$ 53.8