Legal Proceedings and Other Contingencies	12 Months Ended
Legal Proceedings and Other Contingencies	Dec. 31, 2024
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 our 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. Norfolk Southern Train Derailment in East Palestine, Ohio On June 30, 2023, a third-party complaint was filed by Norfolk Southern Railway Company and Norfolk Southern Corporation (collectively, “Norfolk Southern”) against GATX and several other parties in the Northern District of Ohio (Eastern Division) for contribution and recovery of environmental damages related to the derailment of a Norfolk Southern train in East Palestine, Ohio that included railcars owned by GATX Corporation. The Company filed a motion to dismiss Norfolk Southern's third-party complaint on September 15, 2023. On March 6, 2024, the Court granted GATX's and the other third-party defendants’ motions and dismissed all Comprehensive Environmental Response, Compensation and Liability Act ("CERCLA") claims. The Court also dismissed all state law claims, declining to exercise supplemental jurisdiction over them in light of its dismissal of the CERCLA claims. On March 26, 2024, Norfolk Southern moved the Court for entry of partial final judgment as to the order dismissing the third-party complaint in order to appeal before final judgment the Court’s dismissal order as to GATX and the other third-party defendants. The Court has not yet ruled on Norfolk Southern’s motion. In the interim, on May 23, 2024, Norfolk Southern entered into a Consent Decree settling claims with the United States Department of Justice and Environmental Protection Agency (but not the State of Ohio) to which GATX is not a party. On July 25, 2023, a separate third-party complaint was filed by Norfolk Southern against GATX and two other defendants in the Northern District of Ohio (Eastern Division) for contribution to personal injury and property damages class claims related to the derailment of the Norfolk Southern train in East Palestine, Ohio. The plaintiffs who had originally filed the complaint against Norfolk Southern ("Plaintiffs") themselves subsequently filed direct claims against GATX and the two other third-party defendants alleging many of the same facts as Norfolk Southern. On September 15, 2023, the Company filed a motion to dismiss Norfolk Southern's third-party complaint, and on September 26, 2023, filed a motion to dismiss the Plaintiffs' complaint. Briefing was completed on October 30, 2023, and the Court issued an order on March 13, 2024, denying in part, and granting in part, the Company’s motion against Norfolk Southern and Plaintiffs. The Court held that Norfolk Southern’s contribution action was premature and dismissed the claim without prejudice but otherwise allowed the remaining claims against GATX to proceed. The Court also dismissed Plaintiffs’ claim for medical monitoring but held that Plaintiffs could seek such damages through their other claims, which could proceed. The Court also consolidated an additional action filed against GATX and others titled Almasy, et al. v. Norfolk Southern Corp., et al. by over 40 individual residents, employees and property owners in East Palestine, Ohio. Plaintiffs and Norfolk Southern reached a settlement for $600 million to resolve the consolidated class action claims of those within a 20-mile radius from the derailment, and, for those residents who choose to participate, personal injury claims within a 10-mile radius from the derailment. On September 25, 2024, the Court held a final approval hearing and two days later issued its final approval order for the settlement. To date, a handful of appeals challenging the fairness, reasonableness and adequacy of the settlement have been filed with the Sixth Circuit Court of Appeals. On October 9, 2024, all parties to the litigation filed motions for summary judgment for the pending claims. All motions have been fully briefed and are pending. The Court has indicated that rulings are imminent. Norfolk Southern has requested and has been granted leave to reinstate its contribution claims against GATX and others. Trial is currently scheduled for March 31, 2025. On December 8, 2023, GATX and three other defendants were named as additional defendants in a putative class action lawsuit originally filed in federal court in Pennsylvania against Norfolk Southern by four Pennsylvania school districts and their students. The allegations largely mirror those in the action filed in federal court in Ohio. The amended complaint seeks monetary damages for the Pennsylvania plaintiffs for personal injury and property damage allegedly related to the derailment. The Company and other defendants filed a motion to dismiss on February 23, 2024. Briefing has been completed and the motions remain pending and undecided. The Court has not set any further deadlines. GATX recently learned of two new lawsuits filed on February 3, 2025, in the Court of Common Pleas, Franklin County, Ohio on behalf of approximately 750 plaintiffs, of whom approximately 184 have opted out of the prior settlement agreements with Norfolk Southern or were not included and are now suing GATX and approximately 30 other defendants. The remaining plaintiffs who opted into the settlement with Norfolk Southern (approximately 550) are not suing GATX. The Company is vigorously defending itself against each of these lawsuits. At this time, the Company cannot reasonably estimate the loss or range of loss, if any, that may ultimately be incurred in connection with any of these lawsuits and has not established any accruals for potential liability related to this incident. Other Litigation GATX and its subsidiaries have been named as defendants in various 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 our 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. In addition, demand has been made against GATX for asbestos-related claims under limited indemnities given in connection with the sale of certain of our former 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. Litigation Accruals We have recorded accruals totaling $4.9 million at December 31, 2024 for losses related to those litigation matters that we believe to be probable and for which an amount of loss can be reasonably estimated. However, we 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 our 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 we have recorded an accrual, when ultimately resolved, will have a material adverse effect on our 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 our results of operations in a particular quarter or year if such resolution results in liability that materially exceeds the accrued amount. In addition, we have other litigation matters pending for which we have not recorded any accruals because our potential liability for those matters is not probable or cannot be reasonably estimated based on currently available information. For those matters where we have not recorded an accrual but a loss is reasonably possible, we 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 our 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 we have not recorded an accrual, when ultimately resolved, will have a material adverse effect on our 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 our results of operations in a particular quarter or year if such resolution results in a significant liability for GATX. Environmental Our operations are subject to extensive federal, state, and local environmental regulations. Our 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. Under some environmental laws in the U.S. and certain other countries, the owner of a leased transportation asset may be liable for environmental damage and cleanup or other costs in the event of a spill or discharge of material from such asset without regard to the owner’s fault. While our standard forms of lease agreements require the lessee to indemnify us against environmental claims and to carry liability insurance coverage, such indemnities and insurance may not fully protect us against claims for environmental damage. Additionally, some of our 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, we are subject to environmental cleanup and enforcement actions. In particular, 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”), we generally contribute 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 determined to be 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 our internal environmental staff (and where appropriate, independent consultants) have advised 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, we have 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. We conduct 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. We are involved in administrative and judicial proceedings and other voluntary and mandatory cleanup efforts at 9 sites, including Superfund sites, for which we are contributing to the cost of performing the study or cleanup, or both, of alleged environmental contamination. As of December 31, 2024, we have recorded accruals of $12.0 million for remediation and restoration costs that we believe to be probable and for which the amount of loss can be reasonably estimated. These amounts are included in other liabilities on our balance sheet. Our environmental liabilities are not discounted. We did not materially change our 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 our 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, we are 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 our control can impact the amount of loss GATX 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 our consolidated financial position or liquidity.