Investments in Affiliated Companies (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Operating results of affiliated companies of GATX
Revenues	$ 162.6	$ 157.3	$ 336.1	$ 333.4
Pre-tax income reported by affiliates	$ 33.4	$ 11.0	$ 82.5	$ 42.1