Claims, Lawsuits and Other Contingencies	6 Months Ended
Jun. 30, 2025
Commitments and Contingencies Disclosure [Abstract]
Claims, Lawsuits and Other Contingencies	Claims, Lawsuits and Other Contingencies Nature of Contingencies The Company and its subsidiaries are subject to a significant number of claims, lawsuits and proceedings in the course of our business. Such claims and lawsuits consist principally of alleged errors and omissions in connection with the performance of professional services, including the placement of insurance, the provision of actuarial services for corporate and public sector clients, the provision of investment advice and investment management services to pension plans, the provision of advice relating to pension buy-out transactions and the provision of consulting services relating to the drafting and interpretation of trust deeds and other documentation governing pension plans. These claims often seek damages, including punitive and treble damages, in amounts that could be significant. In establishing liabilities for errors and omissions claims, the Company utilizes case level reviews by inside and outside counsel, and internal actuarial analysis by Oliver Wyman Group, a subsidiary of the Company, and other methods to estimate potential losses. A liability is established when a loss is both probable and reasonably estimable. The liability is reviewed quarterly and adjusted as developments warrant. In many cases, the Company has not recorded a liability, other than for legal fees to defend the claim, because we are unable, at the present time, to make a determination that a loss is both probable and reasonably estimable. To the extent that expected losses exceed our deductible in any policy year, the Company also records an asset for the amount that we expect to recover under any available third-party insurance programs. The Company has varying levels of third-party insurance coverage, with policy limits and coverage terms varying significantly by policy year. Our activities are regulated under the laws of the U.S. and its various states, the U.K., the European Union (E.U.) and its member states, Australia and the many other jurisdictions in which the Company operates. The Company also receives subpoenas in the ordinary course of business, and from time to time requests for information in connection with government investigations. Current Matters Risk and Insurance Services Segment •In January 2019, the Company received a notice that the Administrative Council for Economic Defense anti-trust agency in Brazil had commenced an administrative proceeding against a number of insurance brokers, including both Marsh and JLT, and insurers "to investigate an alleged sharing of sensitive commercial and competitive confidential information" in the aviation insurance and reinsurance sector. •From 2014, Marsh Ltd. was engaged by Greensill Capital (UK) Limited and its affiliates as its insurance broker. Marsh Ltd. placed a number of trade credit insurance policies for Greensill. On March 1, 2021, Greensill filed an action against certain of its trade credit insurers in Australia seeking a mandatory injunction compelling these insurers to renew coverage under expiring policies. Later that day, the Australian court denied Greensill’s application. Since then, a number of Greensill entities have filed for, or been subject to, insolvency proceedings, and several litigations and investigations have been commenced in the U.K., Australia, Germany, Switzerland and the U.S., including claims brought by Greensill's administrators and loss payees under Greensill's trade credit insurance policies. The applicants in the omnibus trade credit insurance policy litigation among Greensill and its insurers and loss payees in Australia (the "Australian proceedings") have collectively claimed losses totaling approximately $5 billion plus interest and costs. On June 30, 2025, a court-appointed loss referee delivered a confidential report to the court providing an opinion in respect of the calculation of such alleged losses and the report is under review by the parties. In June 2023, White Oak, a loss payee, filed a claim in the High Court of Justice in London against Marsh Ltd., related to White Oak’s purchase of accounts receivable from Greensill. In May 2025, Marsh Ltd. reached a settlement with White Oak to resolve the matter in the U.K. The settlement was recoverable through the Company's E&O insurance and did not have an impact on the consolidated statements of income for the three and six months ended June 30, 2025. In November 2023, two Credit Suisse funds ("Credit Suisse"), bringing claims as loss payees, added Marsh Ltd. as a party to the Australian proceedings. The claims by Credit Suisse allege that Marsh Ltd. failed to take required steps to ensure representations made to them in their capacity as loss payees were complete and accurate, and that Marsh Ltd. made misleading statements and omissions. In November 2024, Greensill Bank AG (in insolvency), an affiliate of Greensill and an insured entity under the policies, added Marsh Pty Ltd as a party to the Australian proceedings. Greensill Bank subsequently joined Marsh Ltd. to the Australian proceedings in March 2025. Greensill Bank alleges that Marsh Ltd. and Marsh Pty Ltd. did not arrange suitable insurance cover and made misrepresentations regarding trade credit insurance placed for Greensill Bank. The claims in the Australian proceedings are being pursued against a number of parties in addition to Marsh, and the parties are also pursuing (or are expected to pursue) various cross-claims. At this time, the Company is unable to estimate the amount or range of loss due to the complexity of the proceedings, including the number of claims and parties involved. Mediation in the omnibus litigation is expected to begin in the first quarter 2026, with trial currently scheduled for August 2026. Other Contingencies-Guarantees In connection with its acquisition of U.K.-based Sedgwick Group in 1998, the Company acquired several insurance underwriting businesses that were already in run-off, including River Thames Insurance Company Limited ("River Thames"), which the Company sold in 2001. Sedgwick guaranteed payment of claims on certain policies underwritten through the Institute of London Underwriters (the "ILU") by River Thames. The policies covered by this guarantee are partly reinsured by a related party of River Thames. Payment of claims under the reinsurance agreement is collateralized by funds withheld by River Thames from the reinsurer. To the extent River Thames or the reinsurer is unable to meet its obligations under those policies, a claimant may seek to recover from the Company under the guarantee. From 1980 to 1983, the Company owned indirectly the English & American Insurance Company ("E&A"), which was a member of the ILU. The ILU required the Company to guarantee a portion of E&A's obligations. After E&A became insolvent in 1993, the ILU agreed to discharge the guarantee in exchange for the Company's agreement to post an evergreen letter of credit that is available to pay claims by policyholders on certain E&A policies issued through the ILU and incepting between July 3, 1980 and October 6, 1983. Certain claims have been paid under the letter of credit and the Company anticipates that additional claimants may seek to recover against the letter of credit. * * * * * The pending proceedings described above and other matters not explicitly described in this Note 17 on Claims, Lawsuits and Other Contingencies may expose the Company or its subsidiaries to liability for significant monetary damages, fines, penalties or other forms of relief. Where a loss is both probable and reasonably estimable, the Company establishes liabilities in accordance with the Financial Accounting Standards Board ("FASB") guidance on Contingencies - Loss Contingencies. The Company is not able at this time to provide a reasonable estimate of the range of possible loss attributable to these matters or the impact they may have on the Company's consolidated results of operations, financial position or cash flows. This is primarily because these matters are still developing and involve complex issues subject to inherent uncertainty. Adverse determinations in one or more of these matters could have a material impact on the Company's consolidated results of operations, financial condition or cash flows in a future period.

The Company and its subsidiaries are subject to a significant number of claims, lawsuits and proceedings in the course of our business. Such claims and lawsuits consist principally of alleged errors and omissions in connection with the performance of professional services, including the placement of insurance, the provision of actuarial services for corporate and public sector clients, the provision of investment advice and investment management services to pension plans, the provision of advice relating to pension buy-out transactions and the provision of consulting services relating to the drafting and interpretation of trust deeds and other documentation governing pension plans. These claims often seek damages, including punitive and treble damages, in amounts that could be significant. In establishing liabilities for errors and omissions claims, the Company utilizes case level reviews by inside and outside counsel, and internal actuarial analysis by Oliver Wyman Group, a subsidiary of the Company, and other methods to estimate potential losses. A liability is established when a loss is both probable and reasonably estimable. The liability is reviewed quarterly and adjusted as developments warrant. In many cases, the Company has not recorded a liability, other than for legal fees to defend the claim, because we are unable, at the present time, to make a determination that a loss is both probable and reasonably estimable. To the extent that expected losses exceed our deductible in any policy year, the Company also records an asset for the amount that we expect to recover under any available third-party insurance programs. The Company has varying levels of third-party insurance coverage, with policy limits and coverage terms varying significantly by policy year.

•In January 2019, the Company received a notice that the Administrative Council for Economic Defense anti-trust agency in Brazil had commenced an administrative proceeding against a number of insurance brokers, including both Marsh and JLT, and insurers "to investigate an alleged sharing of sensitive commercial and competitive confidential information" in the aviation insurance and reinsurance sector.

•From 2014, Marsh Ltd. was engaged by Greensill Capital (UK) Limited and its affiliates as its insurance broker. Marsh Ltd. placed a number of trade credit insurance policies for Greensill. On March 1, 2021, Greensill filed an action against certain of its trade credit insurers in Australia seeking a mandatory injunction compelling these insurers to renew coverage under expiring policies. Later that day, the Australian court denied Greensill’s application. Since then, a number of Greensill entities have filed for, or been subject to, insolvency proceedings, and several litigations and investigations have been commenced in the U.K., Australia, Germany, Switzerland and the U.S., including claims brought by Greensill's administrators and loss payees under Greensill's trade credit insurance policies. The applicants in the omnibus trade credit insurance policy litigation among Greensill and its insurers and loss payees in Australia (the "Australian proceedings") have collectively claimed losses totaling approximately $5 billion plus interest and costs. On June 30, 2025, a court-appointed loss referee delivered a confidential report to the court providing an opinion in respect of the calculation of such alleged losses and the report is under review by the parties.

In June 2023, White Oak, a loss payee, filed a claim in the High Court of Justice in London against Marsh Ltd., related to White Oak’s purchase of accounts receivable from Greensill. In May 2025, Marsh Ltd. reached a settlement with White Oak to resolve the matter in the U.K. The settlement was recoverable through the Company's E&O insurance and did not have an impact on the consolidated statements of income for the three and six months ended June 30, 2025.

In November 2023, two Credit Suisse funds ("Credit Suisse"), bringing claims as loss payees, added Marsh Ltd. as a party to the Australian proceedings. The claims by Credit Suisse allege that Marsh Ltd. failed to take required steps to ensure representations made to them in their capacity as loss payees were complete and accurate, and that Marsh Ltd. made misleading statements and omissions.

In November 2024, Greensill Bank AG (in insolvency), an affiliate of Greensill and an insured entity under the policies, added Marsh Pty Ltd as a party to the Australian proceedings. Greensill Bank subsequently joined Marsh Ltd. to the Australian proceedings in March 2025. Greensill Bank alleges that Marsh Ltd. and Marsh Pty Ltd. did not arrange suitable insurance cover and made misrepresentations regarding trade credit insurance placed for Greensill Bank.

In connection with its acquisition of U.K.-based Sedgwick Group in 1998, the Company acquired several insurance underwriting businesses that were already in run-off, including River Thames Insurance Company Limited ("River Thames"), which the Company sold in 2001. Sedgwick guaranteed payment of claims on certain policies underwritten through the Institute of London Underwriters (the "ILU") by River Thames. The policies covered by this guarantee are partly reinsured by a related party of River Thames. Payment of claims under the reinsurance agreement is collateralized by funds withheld by River Thames from the reinsurer. To the extent River Thames or the reinsurer is unable to meet its obligations under those policies, a claimant may seek to recover from the Company under the guarantee.

From 1980 to 1983, the Company owned indirectly the English & American Insurance Company ("E&A"), which was a member of the ILU. The ILU required the Company to guarantee a portion of E&A's obligations. After E&A became insolvent in 1993, the ILU agreed to discharge the guarantee in exchange for the Company's agreement to post an evergreen letter of credit that is available to pay claims by policyholders on certain E&A policies issued through the ILU and incepting between July 3, 1980 and October 6, 1983. Certain claims have been paid under the letter of credit and the Company anticipates that additional claimants may seek to recover against the letter of credit.

The pending proceedings described above and other matters not explicitly described in this Note 17 on Claims, Lawsuits and Other Contingencies may expose the Company or its subsidiaries to liability for significant monetary damages, fines, penalties or other forms of relief. Where a loss is both probable and reasonably estimable, the Company establishes liabilities in accordance with the Financial Accounting Standards Board ("FASB") guidance on Contingencies - Loss Contingencies.

The Company is not able at this time to provide a reasonable estimate of the range of possible loss attributable to these matters or the impact they may have on the Company's consolidated results of operations, financial position or cash flows. This is primarily because these matters are still developing and involve complex issues subject to inherent uncertainty. Adverse determinations in one or more of these matters could have a material impact on the Company's consolidated results of operations, financial condition or cash flows in a future period.