Derivative Instruments (Details 1) (Designated as hedging instrument, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
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)
Expected effect during next twelve months	(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
Expected effect during next twelve months	3.1	[1]
Expired hedges | TRIP Holdings warehouse loan
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	2.0		1.5
Expected effect during next twelve months	5.3	[1]
Open hedges | Promissory notes
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	3.9		4.2
Expected effect during next twelve months	16.3	[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
Expected effect during next twelve months	$ 1.7	[1]

[1] Based on the fair value of open hedges as of March 31, 2013