Concentrations	12 Months Ended
Dec. 31, 2012
Risks and Uncertainties [Abstract]
Concentrations	Concentrations Concentration of Revenues — GATX’s revenues are derived from a wide range of industries and companies. Approximately 23% of total revenues are generated from customers in the chemical industry, 20% from the petroleum industry, 15% from transportation industry, 12% from the steel industry and 11% from the food/agriculture industries. GATX’s foreign identifiable revenues were primarily generated in the countries of Canada, Germany, Poland, Mexico and Austria. Concentration of Credit Risk — The Company does not have any revenue concentrations from any particular customer for any of the years ended December 31, 2012, 2011 and 2010. Under its lease agreements with lessees, GATX typically retains legal ownership of the asset except where such assets have been financed by sale-leasebacks. GATX performs a credit evaluation prior to approval of a lease contract. Subsequently, the creditworthiness of the customer and the value of the collateral are monitored on an ongoing basis. GATX maintains an allowance for losses to provide for credit losses inherent in its reservable assets portfolio. Concentration of Labor Force — As of December 31, 2012, 35% of GATX's employees were covered by collective bargaining agreements and 4% of GATX's employees were covered by collective bargaining agreements that have expired or will expire within the next year. The hourly employees at GATX’s U.S. service centers belong to the United Steelworkers. Employees at three of GATX’s Canadian service centers belong to the Communication, Energy and Paperworkers Union of Canada. The shipboard personnel at ASC belong to the American Maritime Officers and the Seafarers International Union.

Concentrations

12 Months Ended

Dec. 31, 2012

Concentration of Revenues — GATX’s revenues are derived from a wide range of industries and companies. Approximately 23% of total revenues are generated from customers in the chemical industry, 20% from the petroleum industry, 15% from transportation industry, 12% from the steel industry and 11% from the food/agriculture industries. GATX’s foreign identifiable revenues were primarily generated in the countries of Canada, Germany, Poland, Mexico and Austria.

Concentration of Credit Risk — The Company does not have any revenue concentrations from any particular customer for any of the years ended December 31, 2012, 2011 and 2010. Under its lease agreements with lessees, GATX typically retains legal ownership of the asset except where such assets have been financed by sale-leasebacks. GATX performs a credit evaluation prior to approval of a lease contract. Subsequently, the creditworthiness of the customer and the value of the collateral are monitored on an ongoing basis. GATX maintains an allowance for losses to provide for credit losses inherent in its reservable assets portfolio.

Concentration of Labor Force — As of December 31, 2012, 35% of GATX's employees were covered by collective bargaining agreements and 4% of GATX's employees were covered by collective bargaining agreements that have expired or will expire within the next year. The hourly employees at GATX’s U.S. service centers belong to the United Steelworkers. Employees at three of GATX’s Canadian service centers belong to the Communication, Energy and Paperworkers Union of Canada. The shipboard personnel at ASC belong to the American Maritime Officers and the Seafarers International Union.