Financial Data of Business Segments (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) Segment	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Lease Income	$ 280.6	$ 274.3	$ 558.9	$ 524.9
Cargo and Freight Revenue	66.0	72.2	90.2	89.9
Provision for Income Taxes, Equity Method Investment	3.0	5.4	$ 6.0	9.6
Number of business segments | Segment			4
Profitability
Other revenue	18.7	19.3	$ 35.9	37.6
Maintenance expense	80.2	84.0	158.5	157.1
Depreciation expense	74.4	71.1	142.9	129.8
Marine operating expense	47.3	54.6	66.2	69.6
Operating lease expense	22.4	27.3	43.1	54.2
Other operating expense	7.8	6.7	15.1	13.3
Total Expenses	232.1	243.7	425.8	424.0
Disposition gains on owned assets	5.1	18.8	43.0	40.4
Residual sharing income	1.6	5.0	3.4	6.8
Nonremarketing disposition gains	2.0	4.4	7.7	9.4
Asset impairment	0.0	0.0	(0.1)	(0.3)
Net gain on asset dispositions	8.7	28.2	54.0	56.3
Interest expense, net	(38.5)	(39.5)	(79.4)	(81.5)
Other (expense) income	(1.6)	(4.9)	(5.6)	(8.3)
Share of affiliates' earnings (pre-tax)	12.0	17.7	23.5	31.8
Segment profit (loss)	113.8	123.6	251.7	226.7
SG&A	44.6	44.9	90.3	87.6
Income tax benefit	20.8	20.2	47.8	34.3
Net Income	45.4	53.1	107.6	95.2
Revenues	365.3	365.8	685.0	652.4
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	175.3	209.6	356.2	655.1
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	368.7		368.7		$ 357.7
Identifiable assets	6,860.0		6,860.0		6,937.5
Rail North America [Member]
Segment Reporting Information [Line Items]
Lease Income	230.9	218.2	459.4	413.1
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	16.8	16.1	$ 31.5	30.7
Maintenance expense	63.8	65.1	133.0	126.5
Depreciation expense	53.3	49.1	105.6	90.6
Marine operating expense	0.0	0.0	0.0	0.0
Operating lease expense	20.7	25.7	41.4	52.6
Other operating expense	5.8	5.2	11.3	10.0
Total Expenses	143.6	145.1	291.3	279.7
Disposition gains on owned assets	5.0	17.7	40.9	39.3
Residual sharing income	0.2	3.8	0.4	4.4
Nonremarketing disposition gains	0.9	2.4	1.6	5.0
Asset impairment	0.0	0.0	0.0	0.0
Net gain on asset dispositions	6.1	23.9	42.9	48.7
Interest expense, net	(24.6)	(25.3)	(49.1)	(49.9)
Other (expense) income	(0.8)	(0.3)	(3.0)	(3.7)
Share of affiliates' earnings (pre-tax)	0.1	4.2	0.3	7.5
Segment profit (loss)	84.9	91.7	190.7	166.7
Revenues	247.7	234.3	490.9	443.8
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	135.2	145.8	265.0	541.8
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	13.4		13.4		17.2
Identifiable assets	4,560.4		4,560.4		4,358.3
Rail International [Member]
Segment Reporting Information [Line Items]
Lease Income	42.4	47.7	84.5	94.9
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	1.7	2.4	$ 3.6	4.4
Maintenance expense	9.4	11.6	18.3	23.1
Depreciation expense	10.8	11.8	21.5	23.5
Marine operating expense	0.0	0.0	0.0	0.0
Operating lease expense	0.1	0.0	0.1	0.0
Other operating expense	1.5	1.0	2.4	2.4
Total Expenses	21.8	24.4	42.3	49.0
Disposition gains on owned assets	0.0	0.6	0.0	0.6
Residual sharing income	0.0	0.0	0.0	0.0
Nonremarketing disposition gains	1.1	2.0	6.1	4.4
Asset impairment	0.0	0.0	(0.1)	0.0
Net gain on asset dispositions	1.1	2.6	6.0	5.0
Interest expense, net	(3.0)	(6.2)	(9.5)	(12.4)
Other (expense) income	(1.2)	(2.7)	(1.2)	(2.7)
Share of affiliates' earnings (pre-tax)	(0.1)	0.0	(0.2)	(0.1)
Segment profit (loss)	19.1	19.4	40.9	40.1
Revenues	44.1	50.1	88.1	99.3
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	27.8	42.3	69.2	81.6
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	1.6		1.6		1.8
Identifiable assets	1,104.9		1,104.9		1,229.4
ASC [Member]
Segment Reporting Information [Line Items]
Lease Income	1.0	1.0	2.0	2.1
Cargo and Freight Revenue	51.0	59.4	$ 58.0	62.5
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	7.0	7.3	7.2	7.5
Depreciation expense	4.9	4.4	4.9	4.4
Marine operating expense	34.1	42.3	41.0	45.7
Operating lease expense	1.7	1.7	1.7	1.7
Other operating expense	0.0	0.0	0.0	0.0
Total Expenses	47.7	55.7	54.8	59.3
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	(0.4)
Net gain on asset dispositions	0.0	0.0	0.0	(0.4)
Interest expense, net	(1.3)	(1.4)	(2.6)	(2.8)
Other (expense) income	(0.1)	(0.2)	(0.1)	(0.2)
Share of affiliates' earnings (pre-tax)	0.0	0.0	0.0	0.0
Segment profit (loss)	2.9	3.1	2.5	1.9
Revenues	52.0	60.4	60.0	64.6
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	10.2	7.7	19.5	16.0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0.0		0.0		0.0
Identifiable assets	307.8		307.8		286.7
Portfolio Management [Member]
Segment Reporting Information [Line Items]
Lease Income	6.3	7.4	13.0	14.8
Cargo and Freight Revenue	15.0	12.8	$ 32.2	27.4
Leverage level expressed as a ratio of recourse debt to equity			3
Profitability
Other revenue	0.2	0.8	$ 0.8	2.5
Maintenance expense	0.0	0.0	0.0	0.0
Depreciation expense	5.4	5.8	10.9	11.3
Marine operating expense	13.2	12.3	25.2	23.9
Operating lease expense	0.0	0.0	0.0	0.0
Other operating expense	0.5	0.5	1.4	0.9
Total Expenses	19.1	18.6	37.5	36.1
Disposition gains on owned assets	0.1	0.5	2.1	0.5
Residual sharing income	1.4	1.2	3.0	2.4
Nonremarketing disposition gains	0.0	0.0	0.0	0.0
Asset impairment	0.0	0.0	0.0	0.1
Net gain on asset dispositions	1.5	1.7	5.1	3.0
Interest expense, net	(5.6)	(6.1)	(10.8)	(12.9)
Other (expense) income	0.0	0.0	0.0	0.3
Share of affiliates' earnings (pre-tax)	12.0	13.5	23.4	24.4
Segment profit (loss)	10.3	11.5	26.2	23.4
Revenues	21.5	21.0	46.0	44.7
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	0.3	12.0	0.3	12.0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	353.7		353.7		338.7
Identifiable assets	796.5		796.5		813.3
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 expense, net	(4.0)	(0.5)	(7.4)	(3.5)
Other (expense) income	0.5	(1.7)	(1.3)	(2.0)
Share of affiliates' earnings (pre-tax)	0.0	0.0	0.0	0.0
Segment profit (loss)	(3.4)	(2.1)	(8.6)	(5.4)
Revenues	0.0	0.0	0.0	0.0
Selected Balance Sheet Data
Portfolio Investments and Capital Additions	1.8	1.8	2.2	3.7
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0.0		0.0		0.0
Identifiable assets	90.4		90.4		$ 249.8
Parent [Member]
Profitability
Income tax benefit	$ 23.8	$ 25.6	$ 53.8	$ 43.9