Derivative Instruments (Details 1) (Designated as hedging instrument, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Expired hedges | TRIP Holdings warehouse loan
Effect on interest expense-increase/(decrease)
Expected effect during next twelve months	$ 4.9
Interest expense | Expired hedges | 2006 secured railcar equipment notes
Effect on interest expense-increase/(decrease)
Effect on interest expense	(0.3)		(0.3)	(0.3)
Expected effect during next twelve months	(0.3)	[1]
Interest expense | Expired hedges | Promissory notes
Effect on interest expense-increase/(decrease)
Effect on interest expense	2.9		3.1	3.3
Expected effect during next twelve months	1.2	[1]
Interest expense | Expired hedges | TRIP Holdings warehouse loan
Effect on interest expense-increase/(decrease)
Effect on interest expense	5.1		6.1	6.0
Expected effect during next twelve months	4.9	[1]
Interest expense | Open hedges | Promissory notes
Effect on interest expense-increase/(decrease)
Effect on interest expense	15.4		15.8	18.4
Expected effect during next twelve months	6.4	[1]
Interest expense | Open hedges | TRIP Master Funding secured railcar equipment notes
Effect on interest expense-increase/(decrease)
Effect on interest expense	1.5		1.8	2.0
Expected effect during next twelve months	$ 1.2	[1]

[1] Based on the fair value of open hedges as of December 31, 2014