Debt (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Maturities of GATX's debt obligations
Debt Principal, 2013	$ 485.7
Debt Principal, 2014	513.6
Debt Principal, 2015	552.5
Debt Principal, 2016	626.9
Debt Principal, 2017	236.2
Debt Principal, Thereafter	866.2
Total Debt	$ 3,281.1	$ 3,498.2

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

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