Derivative Instruments (Details 1) (Designated as Hedging Instrument, USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011	Sep. 30, 2012		Sep. 30, 2011
Expired hedges | 2006 secured railcar equipment notes
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	$ (0.1)		$ (0.1)	$ (0.3)		$ (0.3)
Expected effect during next twelve months	(0.3)	[1]		(0.3)	[1]
Expired hedges | Promissory notes
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	0.8		0.9	2.5		2.7
Expected effect during next twelve months	3.2	[1]		3.2	[1]
Expired hedges | TRIP Holdings
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	1.5		1.8	4.5		15.9
Expected effect during next twelve months	5.9	[1]		5.9	[1]
Open hedges | Promissory notes
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	4.3		4.6	12.7		14.3
Expected effect during next twelve months	17.0	[1]		17.0	[1]
Open hedges | TRIP Master Funding secured railcar equipment notes
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	0.5		0.5	1.5		0.5
Expected effect during next twelve months	$ 1.8	[1]		$ 1.8	[1]

[1] Based on fair value as of September 30, 2012