Debt (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Line of Credit Facility [Line Items]
Non-Recourse Debt	$ 15.9	$ 72.6
Operating assets pledged as collateral for notes	95.9
Other Short-term Borrowings	72.1	23.6
Fixed charge coverage ratio	2.5
Minimum debt covenant fixed charge coverage ratio	1.2
Amount of secured debt available to be borrowed in accordance with public debt covenants	1,283.1
Line of Credit US [Member]
Line of Credit Facility [Line Items]
Unsecured revolving credit facility	575
Availability under credit facility	506.0
Annual commitment fees	0.8	1.0	1.2
Line of Credit Europe [Member]
Line of Credit Facility [Line Items]
Maximum amount of GRE transfer to GATX relating to loans and dividends	111.3
Restricted net assets	391.2
Fair Value Hedging [Member]
Line of Credit Facility [Line Items]
Derivative, Number of Instruments Held	8	3
Commercial Paper [Member]
Line of Credit Facility [Line Items]
Other Short-term Borrowings	$ 69.0