Financial Data of Business Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Profitability
Revenues	$ 343.0	$ 314.6	$ 627.5	$ 579.6
Share of affiliates' earnings	(1.3)	15.0	4.2	32.1
Total Gross Income	341.7	329.6	631.7	611.7
Ownership costs	133.6	133.7	263.3	263.5
Other costs and expenses	130.4	122.8	209.1	212.9
Segment profit (loss)	77.7	73.1	159.3	135.3
SG&A	38.9	37.4	77.0	73.8
Income before Income Taxes	38.8	35.7	82.3	61.5
Capital Expenditures
Portfolio investments and capital additions	238.1	163.9	(391.8)	(260.1)
Selected Balance Sheet Data
Investments in Affiliated Companies	519.5		519.5		513.8
Identifiable assets	5,917.9		5,917.9		5,857.5
Rail [Member]
Profitability
Revenues	246.4	237.7	490.8	474.5
Share of affiliates' earnings	(14.5)	8.3	(16.5)	15.4
Total Gross Income	231.9	246.0	474.3	489.9
Ownership costs	114.1	114.5	228.0	229.5
Other costs and expenses	68.2	74.8	138.1	152.1
Segment profit (loss)	49.6	56.7	108.2	108.3
Capital Expenditures
Portfolio investments and capital additions	176.9	102.4	320.6	156.3
Selected Balance Sheet Data
Investments in Affiliated Companies	128.5		128.5		164.4
Identifiable assets	4,552.2		4,552.2		4,458.2
Financial Data of Business Segments (Textual) [Abstract]
Leverage level expressed as a ratio of recourse debt to equity			4
ASC [Member]
Profitability
Revenues	77.2	58.8	89.0	70.9
Total Gross Income	77.2	58.8	89.0	70.9
Ownership costs	7.0	5.9	8.8	7.9
Other costs and expenses	56.2	44.3	64.1	53.6
Segment profit (loss)	14.0	8.6	16.1	9.4
Capital Expenditures
Portfolio investments and capital additions	5.5	7.4	11.4	12.6
Selected Balance Sheet Data
Identifiable assets	301.4		301.4		286.3
Financial Data of Business Segments (Textual) [Abstract]
Leverage level expressed as a ratio of recourse debt to equity			1.5
Portfolio Management [Member]
Profitability
Revenues	19.1	17.6	47.2	33.5
Share of affiliates' earnings	13.2	6.7	20.7	16.7
Total Gross Income	32.3	24.3	67.9	50.2
Ownership costs	11.8	12.2	24.5	24.0
Other costs and expenses	5.9	3.3	6.8	6.7
Segment profit (loss)	14.6	8.8	36.6	19.5
Capital Expenditures
Portfolio investments and capital additions	53.4	52.9	56.5	89.3
Selected Balance Sheet Data
Investments in Affiliated Companies	391.0		391.0		403.2
Identifiable assets	804.7		804.7		799.5
Financial Data of Business Segments (Textual) [Abstract]
Leverage level expressed as a ratio of recourse debt to equity			3
Other [Member]
Profitability
Revenues	0.3	0.5	0.5	0.7
Total Gross Income	0.3	0.5	0.5	0.7
Ownership costs	0.7	1.1	2.0	2.1
Other costs and expenses	0.1	0.4	0.1	0.5
Segment profit (loss)	(0.5)	(1.0)	(1.6)	(1.9)
Capital Expenditures
Portfolio investments and capital additions	2.3	1.2	3.3	1.9
Selected Balance Sheet Data
Identifiable assets	$ 259.6		$ 259.6		$ 98.5