Derivative Instruments (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Interest Rate Locks, 2005 to 2006 [Member]
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)
Interest Rate Locks, 2006 to 2007 [Member]
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	0.9	0.9
Expected effect during next twelve months	3.3
Interest Rate Locks, TRIP Holdings [Member]
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	1.5	7.3
Expected effect during next twelve months	6.0
Interest Rate Swap TRIP Rail Master Funding Secured Railcar Equipment Notes [Member]
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	0.5
Expected effect during next twelve months	1.9
Interest Rate Swap, 2008 Debt Issuance [Member]
Interest rate hedges effect on interest expense - increase/(decrease)
Effect on interest expense - increase/(decrease)	4.2	4.5
Expected effect during next twelve months	$ 17.4