Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Interest rate hedges included in balance sheet
AOCL - loss/(income)	$ 39.9		$ 46.2
Designated as Hedging Instrument | Expired hedges | 2006 secured railcar equipment notes
Interest rate hedges included in balance sheet
Notional Amount	200.0
Interest Rate	4.87%	[1]
Liability	0
AOCL - loss/(income)	(2.0)
Noncontrolling Interest	0
Designated as Hedging Instrument | Expired hedges | Promissory notes
Interest rate hedges included in balance sheet
Notional Amount	370.0
Interest Rate	5.34%	[1]
Liability	0
AOCL - loss/(income)	8.1
Noncontrolling Interest	0
Designated as Hedging Instrument | Expired hedges | TRIP Holdings
Interest rate hedges included in balance sheet
Notional Amount	788.5
Interest Rate	3.60%	[1]
Liability	0
AOCL - loss/(income)	20.8
Noncontrolling Interest	15.6
Designated as Hedging Instrument | Open hedges | Promissory notes
Interest rate hedges included in balance sheet
Notional Amount	451.7
Interest Rate	4.13%	[1]
Liability	41.9
AOCL - loss/(income)	40.5
Noncontrolling Interest	0
Designated as Hedging Instrument | Open hedges | TRIP Master Funding secured railcar equipment notes
Interest rate hedges included in balance sheet
Notional Amount	81.1
Interest Rate	2.62%	[1]
Liability	5.6
AOCL - loss/(income)	3.2
Noncontrolling Interest	$ 2.3

[1] Weighted average fixed interest rate