Legal Proceedings and Other Contingencies	12 Months Ended
Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Legal Proceedings and Other Contingencies	Legal Proceedings and Other Contingencies Various legal actions, claims, assessments and other contingencies arising in the ordinary course of business are pending against GATX and certain of its subsidiaries. These matters are subject to many uncertainties, and it is possible that some of these matters could ultimately be decided, resolved or settled adversely. Viareggio Derailment On June 29, 2009, a train consisting of fourteen liquefied petroleum gas (“LPG”) tank cars owned by GATX Rail Austria GmbH (an indirect subsidiary of the Company, “GATX Rail Austria”) and its subsidiaries derailed while passing through the city of Viareggio, Italy. Five tank cars overturned and one of the overturned cars was punctured by a peg or obstacle along the side of the track, resulting in a release of LPG, which subsequently ignited. Thirty-two people died and others were injured in the fire, which also resulted in property damage. The LPG tank cars were leased to FS Logistica S.p.A., a subsidiary of the Italian state-owned railway, Ferrovie dello Stato S.p.A (the “Italian Railway”). On June 28, 2012, the Public Prosecutors of Lucca (“Public Prosecutors”) formally notified GATX Rail Austria and two of its subsidiaries (collectively, “GRA”), as well as several maintenance and supervisory employees (the “Employees”), that they had concluded their investigation of the Viareggio accident and intend to charge GRA and the Employees with various negligence-based crimes related to the accident, all of which are punishable under Italian law by incarceration, damages and fines. Similar notices were issued to, among others, four Italian Railway companies and eighteen of their employees. The Public Prosecutor’s report asserts that a crack in one of the tank car’s axles broke, causing the derailment and resulting in a tank car rupture and release of LPG, after the car hit an obstacle on the side of the track placed there by the Italian Railway. The report alleges that the crack was detectable at the time of final inspection but was overlooked by the Employees at the Jungenthal Waggon GmbH workshop (a subsidiary of GATX Rail Austria). The Company believes that GRA and its Employees acted diligently and properly with respect to applicable legal and industry standards and will present numerous scientific and technical defenses to the Public Prosecutor’s report in the forthcoming proceedings. With respect to claims for personal injuries and property damages, the Company and its subsidiaries maintain insurance for such losses, and the Company’s insurers are working cooperatively with the insurer for the Italian Railway to adjust and settle these claims. These joint settlement efforts have resolved the majority of asserted civil damage claims related to the accident, and joint efforts to resolve the remaining civil claims are ongoing. In addition to settling civil claims, the Company’s insurers have been providing reimbursement for legal defense costs, including the costs of criminal defense. One of the Company’s eleven insurers notified the Company that, with respect to its layer of coverage, it will not reimburse the costs of criminal defense, and another insurer has issued a general reservation of rights with respect to coverage of criminal defense costs. The Company is engaged in insurance coverage discussions with its insurers to attempt resolution of the issue. The Company cannot predict the outcome of those discussions or the amount of criminal defense costs that ultimately may not be reimbursed by that insurer. Additionally, the Company cannot predict the outcome of the foregoing legal proceedings or what other legal proceedings, if any, may be initiated against GRA or its personnel, and, therefore, cannot reasonably estimate the amount or range of loss (including criminal defense costs) that may ultimately be incurred in connection with this accident. Accordingly, the Company has not established any accruals with respect to this matter. Other Litigation GATX and its subsidiaries have been named as defendants in various other legal actions and claims, governmental proceedings and private civil suits arising in the ordinary course of business, including environmental matters, workers’ compensation claims and other personal injury claims. Some of these proceedings include claims for punitive as well as compensatory damages. Several of the Company’s subsidiaries have also been named as defendants or co-defendants in cases alleging injury caused by exposure to asbestos. The plaintiffs seek an unspecified amount of damages based on common law, statutory or premises liability or, in the case of ASC, the Jones Act, which provides limited remedies to certain maritime employees. As of January 31, 2013, there were 188 asbestos-related cases pending against the Company and its subsidiaries. Of the total number of pending cases, 156 are Jones Act claims, most of which were filed against ASC before the year 2000. During 2012, 12 new cases were filed, and 18 cases were dismissed without payment or otherwise settled for an immaterial amount. In addition, demand has been made against the Company for asbestos-related claims under limited indemnities given in connection with the sale of certain former subsidiaries of the Company. It is possible that the number of these cases or claims for indemnity could begin to grow and that the cost of these cases, including costs to defend, could correspondingly increase in the future. Litigation Accruals The Company has recorded accruals totaling $2.0 million at December 31, 2012, for losses related to those litigation matters that the Company believes to be probable and for which an amount of loss can be reasonably estimated. However, the Company cannot determine a reasonable estimate of the maximum possible loss or range of loss for these matters given that they are at various stages of the litigation process and each case is subject to the inherent uncertainties of litigation (such as the strength of the Company's legal defenses and the availability of insurance recovery). Although the maximum amount of liability that may ultimately result from any of these matters cannot be predicted with absolute certainty, management expects that none of the matters for which the Company has recorded an accrual, when ultimately resolved, will have a material adverse effect on GATX's consolidated financial position or liquidity. It is possible, however, that the ultimate resolution of one or more of these matters could have a material adverse effect on the Company's results of operations in a particular quarter or year if such resolution results in liability that materially exceeds the accrued amount. In addition, other litigation matters are pending for which the Company has not recorded any accruals because the Company's potential liability for those matters is not probable or cannot be reasonably estimated based on currently available information. For those matters where the Company has not recorded an accrual but a loss is reasonably possible, the Company cannot determine a reasonable estimate of the maximum possible loss or range of loss for these matters given that they are at various stages of the litigation process and each case is subject to the inherent uncertainties of litigation (such as the strength of the Company's legal defenses and the availability of insurance recovery). Although the maximum amount of liability that may ultimately result from any of these matters cannot be predicted with absolute certainty, management expects that none of the matters for which the Company has not recorded an accrual, when ultimately resolved, will have a material adverse effect on GATX's consolidated financial position or liquidity. It is possible, however, that the ultimate resolution of one or more of these matters could have a material adverse effect on the Company's results of operations in a particular quarter or year if such resolution results in a significant liability for the Company. Environmental The Company's operations are subject to extensive federal, state and local environmental regulations. GATX's operating procedures include practices to protect the environment from the risks inherent in full service railcar leasing, which involves maintaining railcars used by customers to transport chemicals and other hazardous materials. Additionally, some of GATX's real estate holdings, including previously owned properties, are or have been used for industrial or transportation-related purposes or leased to commercial or industrial companies whose activities might have resulted in discharges on the property. As a result, GATX is subject to environmental cleanup and enforcement actions. In particular, the federal Comprehensive Environmental Response, Compensation and Liability Act (“CERCLA”), also known as the Superfund law, as well as similar state laws, impose joint and several liability for cleanup and enforcement costs on current and former owners and operators of a site without regard to fault or the legality of the original conduct. If there are other potentially responsible parties (“PRPs”), GATX generally contributes to the cleanup of these sites through cost-sharing agreements with terms that vary from site to site. Costs are typically allocated based on the relative volumetric contribution of material, the period of time the site was owned or operated, and/or the portion of the site owned or operated by each PRP. At the time a potential environmental issue is identified, initial accruals for environmental liability are established when such liability is probable and a reasonable estimate of the associated costs can be made. Costs are estimated based on the type and level of investigation and/or remediation activities that the Company's internal environmental staff (and where appropriate, independent consultants) have determined to be necessary to comply with applicable laws and regulations. Activities include surveys and environmental studies of potentially contaminated sites as well as costs for remediation and restoration of sites determined to be contaminated. In addition, GATX has provided indemnities for potential environmental liabilities to buyers of divested companies. In these instances, accruals are based on the scope and duration of the respective indemnities together with the extent of known contamination. Estimates are periodically reviewed and adjusted as required to reflect additional information about facility or site characteristics or changes in regulatory requirements. GATX conducts a quarterly environmental contingency analysis, which considers a combination of factors including independent consulting reports, site visits, legal reviews, analysis of the likelihood of participation in and the ability of other PRPs to pay for cleanup, and historical trend analyses. GATX is involved in administrative and judicial proceedings and other voluntary and mandatory cleanup efforts at 17 sites, including Superfund sites, at which it is contributing to the cost of performing the study or cleanup, or both, of alleged environmental contamination. As of December 31, 2012, GATX has recorded accruals of $15.6 million for remediation and restoration costs that the Company believes to be probable and for which the amount of loss can be reasonably estimated. These amounts are included in other liabilities on GATX's balance sheet. GATX's environmental liabilities are not discounted. The Company did not materially change its methodology for identifying and calculating environmental liabilities in the last three years. Currently, no known trends, demands, commitments, events or uncertainties exist that are reasonably likely to occur and materially affect the methodology or assumptions described above. The recorded accruals represent the Company's best estimate of all costs for remediation and restoration of affected sites, without reduction for anticipated recoveries from third parties, and include both asserted and unasserted claims. However, the Company is unable to provide a reasonable estimate of the maximum potential loss associated with these sites because cleanup costs cannot be predicted with certainty. Various factors beyond the Company's control can impact the amount of loss the Company will ultimately incur with respect to these sites, including the extent of corrective actions that may be required; evolving environmental laws and regulations; advances in environmental technology, the extent of other parties' participation in cleanup efforts; developments in periodic environmental analyses related to sites determined to be contaminated, and developments in environmental surveys and studies of potentially contaminated sites. As a result, future charges associated with these sites could have a significant effect on results of operations in a particular quarter or year if the costs materially exceed the accrued amount as individual site studies and remediation and restoration efforts proceed. However, management believes it is unlikely that the ultimate cost to GATX for any of these sites, either individually or in the aggregate, will have a material adverse effect on GATX's consolidated financial position or liquidity.

Legal Proceedings and Other Contingencies

Various legal actions, claims, assessments and other contingencies arising in the ordinary course of business are pending against GATX and certain of its subsidiaries. These matters are subject to many uncertainties, and it is possible that some of these matters could ultimately be decided, resolved or settled adversely.

Viareggio Derailment

On June 29, 2009, a train consisting of fourteen liquefied petroleum gas (“LPG”) tank cars owned by GATX Rail Austria GmbH (an indirect subsidiary of the Company, “GATX Rail Austria”) and its subsidiaries derailed while passing through the city of Viareggio, Italy. Five tank cars overturned and one of the overturned cars was punctured by a peg or obstacle along the side of the track, resulting in a release of LPG, which subsequently ignited. Thirty-two people died and others were injured in the fire, which also resulted in property damage. The LPG tank cars were leased to FS Logistica S.p.A., a subsidiary of the Italian state-owned railway, Ferrovie dello Stato S.p.A (the “Italian Railway”). On June 28, 2012, the Public Prosecutors of Lucca (“Public Prosecutors”) formally notified GATX Rail Austria and two of its subsidiaries (collectively, “GRA”), as well as several maintenance and supervisory employees (the “Employees”), that they had concluded their investigation of the Viareggio accident and intend to charge GRA and the Employees with various negligence-based crimes related to the accident, all of which are punishable under Italian law by incarceration, damages and fines. Similar notices were issued to, among others, four Italian Railway companies and eighteen of their employees. The Public Prosecutor’s report asserts that a crack in one of the tank car’s axles broke, causing the derailment and resulting in a tank car rupture and release of LPG, after the car hit an obstacle on the side of the track placed there by the Italian Railway. The report alleges that the crack was detectable at the time of final inspection but was overlooked by the Employees at the Jungenthal Waggon GmbH workshop (a subsidiary of GATX Rail Austria). The Company believes that GRA and its Employees acted diligently and properly with respect to applicable legal and industry standards and will present numerous scientific and technical defenses to the Public Prosecutor’s report in the forthcoming proceedings. With respect to claims for personal injuries and property damages, the Company and its subsidiaries maintain insurance for such losses, and the Company’s insurers are working cooperatively with the insurer for the Italian Railway to adjust and settle these claims. These joint settlement efforts have resolved the majority of asserted civil damage claims related to the accident, and joint efforts to resolve the remaining civil claims are ongoing. In addition to settling civil claims, the Company’s insurers have been providing reimbursement for legal defense costs, including the costs of criminal defense. One of the Company’s eleven insurers notified the Company that, with respect to its layer of coverage, it will not reimburse the costs of criminal defense, and another insurer has issued a general reservation of rights with respect to coverage of criminal defense costs. The Company is engaged in insurance coverage discussions with its insurers to attempt resolution of the issue. The Company cannot predict the outcome of those discussions or the amount of criminal defense costs that ultimately may not be reimbursed by that insurer. Additionally, the Company cannot predict the outcome of the foregoing legal proceedings or what other legal proceedings, if any, may be initiated against GRA or its personnel, and, therefore, cannot reasonably estimate the amount or range of loss (including criminal defense costs) that may ultimately be incurred in connection with this accident. Accordingly, the Company has not established any accruals with respect to this matter.

Other Litigation

GATX and its subsidiaries have been named as defendants in various other legal actions and claims, governmental proceedings and private civil suits arising in the ordinary course of business, including environmental matters, workers’ compensation claims and other personal injury claims. Some of these proceedings include claims for punitive as well as compensatory damages.

Several of the Company’s subsidiaries have also been named as defendants or co-defendants in cases alleging injury caused by exposure to asbestos. The plaintiffs seek an unspecified amount of damages based on common law, statutory or premises liability or, in the case of ASC, the Jones Act, which provides limited remedies to certain maritime employees. As of January 31, 2013, there were 188 asbestos-related cases pending against the Company and its subsidiaries. Of the total number of pending cases, 156 are Jones Act claims, most of which were filed against ASC before the year 2000. During 2012, 12 new cases were filed, and 18 cases were dismissed without payment or otherwise settled for an immaterial amount. In addition, demand has been made against the Company for asbestos-related claims under limited indemnities given in connection with the sale of certain former subsidiaries of the Company. It is possible that the number of these cases or claims for indemnity could begin to grow and that the cost of these cases, including costs to defend, could correspondingly increase in the future.

Litigation Accruals

The Company has recorded accruals totaling $2.0 million at December 31, 2012, for losses related to those litigation matters that the Company believes to be probable and for which an amount of loss can be reasonably estimated. However, the Company cannot determine a reasonable estimate of the maximum possible loss or range of loss for these matters given that they are at various stages of the litigation process and each case is subject to the inherent uncertainties of litigation (such as the strength of the Company's legal defenses and the availability of insurance recovery). Although the maximum amount of liability that may ultimately result from any of these matters cannot be predicted with absolute certainty, management expects that none of the matters for which the Company has recorded an accrual, when ultimately resolved, will have a material adverse effect on GATX's consolidated financial position or liquidity. It is possible, however, that the ultimate resolution of one or more of these matters could have a material adverse effect on the Company's results of operations in a particular quarter or year if such resolution results in liability that materially exceeds the accrued amount.

In addition, other litigation matters are pending for which the Company has not recorded any accruals because the Company's potential liability for those matters is not probable or cannot be reasonably estimated based on currently available information. For those matters where the Company has not recorded an accrual but a loss is reasonably possible, the Company cannot determine a reasonable estimate of the maximum possible loss or range of loss for these matters given that they are at various stages of the litigation process and each case is subject to the inherent uncertainties of litigation (such as the strength of the Company's legal defenses and the availability of insurance recovery). Although the maximum amount of liability that may ultimately result from any of these matters cannot be predicted with absolute certainty, management expects that none of the matters for which the Company has not recorded an accrual, when ultimately resolved, will have a material adverse effect on GATX's consolidated financial position or liquidity. It is possible, however, that the ultimate resolution of one or more of these matters could have a material adverse effect on the Company's results of operations in a particular quarter or year if such resolution results in a significant liability for the Company.

Environmental

The Company's operations are subject to extensive federal, state and local environmental regulations. GATX's operating procedures include practices to protect the environment from the risks inherent in full service railcar leasing, which involves maintaining railcars used by customers to transport chemicals and other hazardous materials. Additionally, some of GATX's real estate holdings, including previously owned properties, are or have been used for industrial or transportation-related purposes or leased to commercial or industrial companies whose activities might have resulted in discharges on the property. As a result, GATX is subject to environmental cleanup and enforcement actions. In particular, the federal Comprehensive Environmental Response, Compensation and Liability Act (“CERCLA”), also known as the Superfund law, as well as similar state laws, impose joint and several liability for cleanup and enforcement costs on current and former owners and operators of a site without regard to fault or the legality of the original conduct. If there are other potentially responsible parties (“PRPs”), GATX generally contributes to the cleanup of these sites through cost-sharing agreements with terms that vary from site to site. Costs are typically allocated based on the relative volumetric contribution of material, the period of time the site was owned or operated, and/or the portion of the site owned or operated by each PRP.

At the time a potential environmental issue is identified, initial accruals for environmental liability are established when such liability is probable and a reasonable estimate of the associated costs can be made. Costs are estimated based on the type and level of investigation and/or remediation activities that the Company's internal environmental staff (and where appropriate, independent consultants) have determined to be necessary to comply with applicable laws and regulations. Activities include surveys and environmental studies of potentially contaminated sites as well as costs for remediation and restoration of sites determined to be contaminated. In addition, GATX has provided indemnities for potential environmental liabilities to buyers of divested companies. In these instances, accruals are based on the scope and duration of the respective indemnities together with the extent of known contamination. Estimates are periodically reviewed and adjusted as required to reflect additional information about facility or site characteristics or changes in regulatory requirements. GATX conducts a quarterly environmental contingency analysis, which considers a combination of factors including independent consulting reports, site visits, legal reviews, analysis of the likelihood of participation in and the ability of other PRPs to pay for cleanup, and historical trend analyses.

GATX is involved in administrative and judicial proceedings and other voluntary and mandatory cleanup efforts at 17 sites, including Superfund sites, at which it is contributing to the cost of performing the study or cleanup, or both, of alleged environmental contamination. As of December 31, 2012, GATX has recorded accruals of $15.6 million for remediation and restoration costs that the Company believes to be probable and for which the amount of loss can be reasonably estimated. These amounts are included in other liabilities on GATX's balance sheet. GATX's environmental liabilities are not discounted.

The Company did not materially change its methodology for identifying and calculating environmental liabilities in the last three years. Currently, no known trends, demands, commitments, events or uncertainties exist that are reasonably likely to occur and materially affect the methodology or assumptions described above.

The recorded accruals represent the Company's best estimate of all costs for remediation and restoration of affected sites, without reduction for anticipated recoveries from third parties, and include both asserted and unasserted claims. However, the Company is unable to provide a reasonable estimate of the maximum potential loss associated with these sites because cleanup costs cannot be predicted with certainty. Various factors beyond the Company's control can impact the amount of loss the Company will ultimately incur with respect to these sites, including the extent of corrective actions that may be required; evolving environmental laws and regulations; advances in environmental technology, the extent of other parties' participation in cleanup efforts; developments in periodic environmental analyses related to sites determined to be contaminated, and developments in environmental surveys and studies of potentially contaminated sites. As a result, future charges associated with these sites could have a significant effect on results of operations in a particular quarter or year if the costs materially exceed the accrued amount as individual site studies and remediation and restoration efforts proceed. However, management believes it is unlikely that the ultimate cost to GATX for any of these sites, either individually or in the aggregate, will have a material adverse effect on GATX's consolidated financial position or liquidity.