Leases (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Minimum Future Receipts
2013, Finance Leases	$ 40.2
2014, Finance Leases	38.7
2015, Finance Leases	35.9
2016, Finance Leases	31.3
2017, Finance Leases	29.4
Years thereafter, Finance Leases	151.8
Total, Finance Leases	327.3
2013, Operating Leases	784.4	[1]
2014, Operating Leases	594.2	[1]
2015, Operating Leases	465.8	[1]
2016, Operating Leases	346.1	[1]
2017, Operating Leases	223.0	[1]
Years thereafter, Operating Leases	461.7	[1]
Total future receipts from leases	2,875.2	[1]
2013, Total	824.6
2014, Total	632.9
2015, Total	501.7
2016, Total	377.4
2017, Total	252.4
Years thereafter, Total	613.5
Total	$ 3,202.5

[1] The future contractual receipts due under operating leases include executory costs in the case of GATX's full service leases.