Financial Data of Business Segments (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) Segment	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Lease Income	$ 281.8	$ 286.2	$ 847.5	$ 845.1
Cargo and Freight Revenue	62.1	77.6	139.7	167.8
Provision for Income Taxes, Equity Method Investment	(0.1)	(2.8)	$ 4.0	3.2
Number of business segments | Segment			4
Profitability
Other revenue	19.0	22.4	$ 69.0	58.3
Maintenance expense	79.6	83.9	244.6	242.4
Depreciation expense	75.9	75.0	221.0	217.9
Marine operating expense	39.2	48.5	88.9	114.7
Operating lease expense	(19.2)	(22.3)	(54.5)	(65.4)
Other operating expense	10.1	8.3	33.7	23.4
Total Expenses	224.0	238.0	642.7	663.8
Disposition gains on owned assets	11.6	17.4	36.7	60.4
Residual sharing income	49.7	7.6	83.2	11.0
Nonremarketing disposition gains	1.4	1.6	4.7	9.3
Asset impairment		(31.1)	(1.8)	(31.2)
Net gain on asset dispositions	62.7	(4.5)	122.8	49.5
Interest Revenue (Expense), Net	(36.2)	(37.7)	(109.9)	(117.1)
Other (expense) income	(4.3)	3.1	2.9	8.7
Income (Loss) From Equity Method Investment, Before Tax	15.1	(1.5)	33.1	22.0
Segment profit (loss)	184.8	101.4	456.6	353.1
SG&A	48.1	44.4	127.8	134.7
Income tax benefit	41.1	20.3	98.6	68.1
Net Income	95.7	39.5	226.2	147.1
Revenues	362.9	386.2	1,056.2	1,071.2
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	120.4	142.1	442.6	498.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	376.8		376.8		$ 348.5
Identifiable assets	7,089.3		7,089.3		6,894.2
Rail North America [Member]
Segment Reporting Information [Line Items]
Lease Income	233.0	234.9	703.0	694.3
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	17.3	20.3	$ 63.5	51.8
Maintenance expense	62.8	66.7	196.2	199.7
Depreciation expense	58.4	54.5	173.0	160.1
Marine operating expense	0.0	0.0	0.0	0.0
Operating lease expense	(17.2)	(20.6)	(50.6)	(62.0)
Other operating expense	8.6	6.8	25.0	18.1
Total Expenses	147.0	148.6	444.8	439.9
Disposition gains on owned assets	11.9	10.2	32.5	51.1
Residual sharing income	0.3	0.3	0.7	0.7
Nonremarketing disposition gains	0.9	1.0	3.2	2.6
Asset impairment		0.0	0.0	0.0
Net gain on asset dispositions	13.1	11.5	36.4	54.4
Interest Revenue (Expense), Net	(27.1)	(27.0)	(81.2)	(76.1)
Other (expense) income	1.4	1.2	3.8	4.2
Income (Loss) From Equity Method Investment, Before Tax	0.0	0.1	0.3	0.4
Segment profit (loss)	87.9	90.0	273.4	280.7
Revenues	250.3	255.2	766.5	746.1
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	108.4	97.8	366.7	362.8
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	10.5		10.5		12.0
Identifiable assets	4,792.7		4,792.7		4,629.1
Rail International [Member]
Segment Reporting Information [Line Items]
Lease Income	46.6	44.1	136.8	128.6
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	$ 4.8	5.3
Maintenance expense	10.7	9.9	36.1	28.2
Depreciation expense	11.6	11.1	34.2	32.6
Marine operating expense	0.0	0.0	0.0	0.0
Operating lease expense	0.0	0.1	0.0	0.0
Other operating expense	1.2	1.1	3.8	3.5
Total Expenses	23.5	22.0	74.1	64.3
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	0.5	0.6	1.5	6.7
Asset impairment		(0.1)	0.0	(0.2)
Net gain on asset dispositions	0.5	0.5	1.5	6.5
Interest Revenue (Expense), Net	(7.3)	(7.0)	(21.9)	(16.5)
Other (expense) income	(5.5)	1.8	(2.0)	3.0
Income (Loss) From Equity Method Investment, Before Tax	(0.1)	0.0	(0.2)	(0.2)
Segment profit (loss)	23.3	15.5	48.9	56.4
Revenues	48.2	45.8	141.6	133.9
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	10.8	40.9	63.2	110.1
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	1.3		1.3		1.4
Identifiable assets	1,183.9		1,183.9		1,117.6
ASC [Member]
Segment Reporting Information [Line Items]
Lease Income	1.0	1.1	3.1	3.1
Cargo and Freight Revenue	51.8	61.7	$ 102.3	119.7
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	6.1	7.3	12.3	14.5
Depreciation expense	4.2	4.7	8.6	9.6
Marine operating expense	31.5	36.7	64.0	77.7
Operating lease expense	(2.0)	(1.8)	(4.0)	(3.5)
Other operating expense	0.0	0.0	0.0	0.0
Total Expenses	43.8	50.5	88.9	105.3
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	0.0	0.0	0.0	0.0
Asset impairment		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)	(1.4)	(3.3)	(4.0)
Other (expense) income	0.1	0.0	0.3	0.1
Income (Loss) From Equity Method Investment, Before Tax	0.0	0.0	0.0	0.0
Segment profit (loss)	7.8	10.9	12.9	13.4
Revenues	52.8	62.8	105.4	122.8
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	0.0	0.8	9.1	20.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0.0		0.0		0.0
Identifiable assets	285.6		285.6		284.7
Portfolio Management [Member]
Segment Reporting Information [Line Items]
Lease Income	1.2	6.1	4.6	19.1
Cargo and Freight Revenue	10.3	15.9	$ 37.4	48.1
Leverage level expressed as a ratio of recourse debt to equity			3
Profitability
Other revenue	0.1	0.4	$ 0.7	1.2
Maintenance expense	0.0	0.0	0.0	0.0
Depreciation expense	1.7	4.7	5.2	15.6
Marine operating expense	7.7	11.8	24.9	37.0
Operating lease expense	0.0	0.0	0.0	0.0
Other operating expense	0.3	0.4	4.9	1.8
Total Expenses	9.7	16.9	35.0	54.4
Disposition gains on owned assets	(0.3)	7.2	4.2	9.3
Residual sharing income	49.4	7.3	82.5	10.3
Nonremarketing disposition gains	0.0	0.0	0.0	0.0
Asset impairment		(31.0)	(1.8)	(31.0)
Net gain on asset dispositions	49.1	(16.5)	84.9	(11.4)
Interest Revenue (Expense), Net	(2.1)	(4.7)	(6.4)	(15.5)
Other (expense) income	0.0	0.0	0.0	0.0
Income (Loss) From Equity Method Investment, Before Tax	15.2	(1.6)	33.0	21.8
Segment profit (loss)	64.1	(17.3)	119.2	8.9
Revenues	11.6	22.4	42.7	68.4
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	0.0	1.9	0.0	2.2
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	365.0		365.0		335.1
Identifiable assets	606.2		606.2		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	0.0	0.0	0.1	0.1
Other operating expense	0.0	0.0	0.0	0.0
Total Expenses	0.0	0.0	(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
Net gain on asset dispositions	0.0	0.0	0.0	0.0
Interest Revenue (Expense), Net	1.4	2.4	2.9	(5.0)
Other (expense) income	(0.3)	0.1	0.8	1.4
Income (Loss) From Equity Method Investment, Before Tax	0.0	0.0	0.0	0.0
Segment profit (loss)	1.7	2.3	2.2	(6.3)
Revenues	0.0	0.0	0.0	0.0
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	1.2	0.7	3.6	2.9
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0.0		0.0		0.0
Identifiable assets	220.9		220.9		$ 226.3
Parent [Member]
Profitability
Income tax benefit	$ 41.0	17.5	$ 102.6	71.3
Cardinal Marine [Domain]
Profitability
Asset impairment		$ 19.0		$ 19.0