Derivative Instruments - Effect on statements of operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest rate swap, Expired, TRIP Holdings warehouse loan
Derivative [Line Items]
Expected effect during next twelve months	$ 2.1
Interest Rate Cap [Member]
Derivative [Line Items]
Expected effect during next twelve months	0.2
Interest expense | Designated as hedging instrument | Interest rate swap, Expired, 2006 secured railcar equipment notes
Derivative [Line Items]
Expired hedges	(0.2)	$ (0.3)	$ (0.4)
Expected effect during next twelve months	0.1
Interest expense | Designated as hedging instrument | Interest Rate Swap, Expired, 2018 Secured Railcar Equipment Notes [Member]
Derivative [Line Items]
Expired hedges	(0.1)	0.0	0.0
Expected effect during next twelve months	(0.2)
Interest expense | Designated as hedging instrument | Interest rate swap, Expired, TRIP Holdings warehouse loan
Derivative [Line Items]
Expired hedges	2.2	4.5	4.8
Expected effect during next twelve months	2.1
Interest expense | Designated as hedging instrument | Interest Rate Swap, Open, TRIP Master Funding secured railcar equipment notes
Derivative [Line Items]
Open hedges	0.2	0.4	0.9
Expected effect during next twelve months	0.2
Interest expense | Designated as hedging instrument | Interest Rate Cap [Member]
Derivative [Line Items]
Expired hedges	0.1	0.0	0.0
Expected effect during next twelve months	0.1
Interest expense | Designated as hedging instrument | Interest Rate Swap [Member]
Derivative [Line Items]
Expired hedges	0.3	$ 0.0	$ 0.0
Expected effect during next twelve months	$ 0.1