Marsh & McLennan Companies (MMC) 10-Q 18 Jul 24 2024 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2024	Jul. 15, 2024
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
Document Transition Report	false
Entity Registrant Name	Marsh & McLennan Companies, Inc.
Entity Address, Address Line One	1166 Avenue of the Americas
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10036
City Area Code	212
Local Phone Number	345-5000
Entity File Number	1-5998
Entity Address, State or Province	DE
Entity Tax Identification Number	36-2668272
Title of 12(b) Security	Common Stock, par value $1.00 per share
Trading Symbol	MMC
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		491,755,908
Entity Central Index Key	0000062709
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Amendment Flag	false
New York Stock Exchange
Entity Information [Line Items]
Security Exchange Name	NYSE
Chicago Stock Exchange
Entity Information [Line Items]
Security Exchange Name	CHX

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
Revenue	$ 6,221	$ 5,876	$ 12,694	$ 11,800
Expense:
Compensation and benefits	3,454	3,337	6,924	6,544
Other operating expenses	1,125	1,082	2,203	2,073
Operating expenses	4,579	4,419	9,127	8,617
Operating income	1,642	1,457	3,567	3,183
Other net benefit credits	66	60	133	118
Interest income	12	10	49	24
Interest expense	(156)	(146)	(315)	(282)
Investment income	1	3	2	5
Income before income taxes	1,565	1,384	3,436	3,048
Income tax expense	425	337	872	749
Net income before non-controlling interests	1,140	1,047	2,564	2,299
Less: Net income attributable to non-controlling interests	15	12	39	29
Net income attributable to the Company	$ 1,125	$ 1,035	$ 2,525	$ 2,270
Net income per share attributable to the Company:
Basic (in dollars per share)	$ 2.28	$ 2.09	$ 5.13	$ 4.59
Diluted (in dollars per share)	$ 2.27	$ 2.07	$ 5.08	$ 4.55
Average number of shares outstanding:
Basic (in shares)	492	495	492	495
Diluted (in shares)	496	499	497	499
Shares outstanding (in shares)	492	494	492	494

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income before non-controlling interests	$ 1,140	$ 1,047	$ 2,564	$ 2,299
Other comprehensive (loss) income, before tax:
Foreign currency translation adjustments	(28)	223	(272)	342
Gain (loss) related to pension/post-retirement plans	18	(62)	68	(120)
Other comprehensive (loss) income before tax	(10)	161	(204)	222
Income tax expense (benefit) on other comprehensive loss	8	(18)	28	(37)
Other comprehensive (loss) income, net of tax	(18)	179	(232)	259
Comprehensive income	1,122	1,226	2,332	2,558
Less: comprehensive income attributable to non-controlling interest	15	12	39	29
Comprehensive income attributable to the Company	$ 1,107	$ 1,214	$ 2,293	$ 2,529

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 1,653	$ 3,358
Cash and cash equivalents held in a fiduciary capacity	11,497	10,794
Receivables
Commissions and fees	7,031	5,806
Advanced premiums and claims	119	103
Other	749	660
Gross receivables	7,899	6,569
Less-allowance for credit losses	(160)	(151)
Net receivables	7,739	6,418
Other current assets	1,133	1,178
Total current assets	22,022	21,748
Goodwill	17,516	17,231
Other intangible assets	2,638	2,630
Fixed assets (net of accumulated depreciation and amortization of $1,572 at June 30, 2024 and $1,562 at December 31, 2023)	879	882
Pension related assets	2,187	2,051
Right of use assets	1,468	1,541
Deferred tax assets	285	357
Other assets	1,596	1,590
Total assets	48,591	48,030
Current liabilities:
Short-term debt	1,267	1,619
Accounts payable and accrued liabilities	3,205	3,403
Accrued compensation and employee benefits	2,086	3,346
Current lease liabilities	304	312
Accrued income taxes	505	321
Fiduciary liabilities	11,497	10,794
Total current liabilities	18,864	19,795
Long-term debt	12,278	11,844
Pension, post-retirement and post-employment benefits	715	779
Long-term lease liabilities	1,586	1,661
Liabilities for errors and omissions	322	314
Other liabilities	1,261	1,267
Commitments and contingencies	0	0
Equity:
Preferred stock, $1 par value, authorized 6,000,000 shares, none issued	0	0
Common stock, $1 par value, authorized 1,600,000,000 shares, issued 560,641,640 shares at June 30, 2024 and December 31, 2023	561	561
Additional paid-in capital	1,197	1,242
Retained earnings	24,578	22,759
Accumulated other comprehensive loss	(5,527)	(5,295)
Non-controlling interests	198	179
Stockholders' equity before treasury stock	21,007	19,446
Less – treasury shares, at cost, 68,717,711 shares at June 30, 2024 and 68,635,498 shares at December 31, 2023	(7,442)	(7,076)
Total equity	13,565	12,370
Total liabilities and stockholders' equity	$ 48,591	$ 48,030

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Fixed assets, accumulated depreciation and amortization	$ 1,572	$ 1,562
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	6,000,000	6,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	1,600,000,000	1,600,000,000
Common stock, shares issued (in shares)	560,641,640	560,641,640
Treasury stock, shares (in shares)	68,717,711	68,635,498

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Operating cash flows:
Net income before non-controlling interests	$ 2,564	$ 2,299
Adjustments to reconcile net income provided by operations:
Depreciation and amortization of fixed assets and capitalized software	186	175
Amortization of intangible assets	179	172
Non-cash lease expense	132	143
Adjustments and payments related to contingent consideration assets and liabilities	(75)	(23)
Net gain on investments	(2)	(5)
Net (gain) loss on disposition of assets	(20)	19
Share-based compensation expense	193	191
Changes in assets and liabilities:
Net receivables	(1,287)	(1,029)
Other assets	(62)	(108)
Accrued compensation and employee benefits	(1,226)	(1,101)
Provision for taxes, net of payments and refunds	214	245
Contributions to pension and other benefit plans in excess of current year credit	(182)	(164)
Other liabilities	(30)	10
Operating lease liabilities	(150)	(159)
Net cash provided by operations	434	665
Financing cash flows:
Purchase of treasury shares	(600)	(600)
Net proceeds from issuance of commercial paper	749	308
Borrowings from term-loan and credit facilities	0	200
Proceeds from issuance of debt	988	589
Repayments of debt	(1,609)	(8)
Purchase of non-controlling interests	0	(139)
Shares withheld for taxes on vested units – treasury shares	(173)	(141)
Issuance of common stock from treasury shares	167	120
Payments of deferred and contingent consideration for acquisitions	(81)	(185)
Receipts of contingent consideration for dispositions	1	2
Distributions of non-controlling interests	(21)	(10)
Dividends paid	(706)	(591)
Change in fiduciary liabilities	901	682
Net cash (used for) provided by financing activities	(384)	227
Investing cash flows:
Capital expenditures	(167)	(185)
Purchases of long term investments	(14)	(30)
Sales of long term investments	14	16
Dispositions	27	(17)
Acquisitions, net of cash and cash held in a fiduciary capacity acquired	(644)	(292)
Other, net	1	7
Net cash used for investing activities	(783)	(501)
Effect of exchange rate changes on cash, cash equivalents, and cash and cash equivalents held in a fiduciary capacity	(269)	242
(Decrease)/increase in cash, cash equivalents, and cash and cash equivalents held in a fiduciary capacity	(1,002)	633
Cash, cash equivalents, and cash and cash equivalents held in a fiduciary capacity at beginning of period	14,152	12,102
Cash, cash equivalents, and cash and cash equivalents held in a fiduciary capacity at end of period	13,150	12,735
Cash and cash equivalents	1,653	1,171
Cash and cash equivalents held in a fiduciary capacity	11,497	11,564
Total cash, cash equivalents, and cash and cash equivalents held in a fiduciary capacity	$ 13,150	$ 12,735

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Millions	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	RETAINED EARNINGS	ACCUMULATED OTHER COMPREHENSIVE LOSS	TREASURY SHARES	NON-CONTROLLING INTERESTS
Balance, beginning of period at Dec. 31, 2022		$ 561	$ 1,179	$ 20,301	$ (5,314)	$ (6,207)	$ 229
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in accrued stock compensation costs			(101)
Issuance of shares under stock compensation plans and employee stock purchase plans			66			208
Purchase of non-controlling interest			(70)
Net income attributable to the Company	$ 2,299			2,270			29
Dividend equivalents declared				(8)
Dividends declared				(583)
Other comprehensive (loss) income, net of tax	259				259
Purchase of treasury shares	(600)					(600)
Net non-controlling interests acquired							(69)
Distributions and other changes							(11)
Balance, end of period at Jun. 30, 2023	$ 12,139		1,074	21,980	(5,055)	(6,599)	178
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in dollars per share)	$ 1.18
Balance, beginning of period at Mar. 31, 2023		561	1,064	20,949	(5,234)	(6,387)	243
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in accrued stock compensation costs			89
Issuance of shares under stock compensation plans and employee stock purchase plans			(9)			88
Purchase of non-controlling interest			(70)
Net income attributable to the Company	$ 1,047			1,035			12
Dividend equivalents declared				(4)
Dividends declared				0
Other comprehensive (loss) income, net of tax	179				179
Purchase of treasury shares						(300)
Net non-controlling interests acquired							(69)
Distributions and other changes							(8)
Balance, end of period at Jun. 30, 2023	$ 12,139		1,074	21,980	(5,055)	(6,599)	178
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in dollars per share)	$ 0
Balance, beginning of period at Dec. 31, 2023	$ 12,370	561	1,242	22,759	(5,295)	(7,076)	179
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in accrued stock compensation costs			(125)
Issuance of shares under stock compensation plans and employee stock purchase plans			80			234
Purchase of non-controlling interest			0
Net income attributable to the Company	2,564			2,525			39
Dividend equivalents declared				(7)
Dividends declared				(699)
Other comprehensive (loss) income, net of tax	(232)				(232)
Purchase of treasury shares	(600)					(600)
Net non-controlling interests acquired							0
Distributions and other changes							(20)
Balance, end of period at Jun. 30, 2024	$ 13,565		1,197	24,578	(5,527)	(7,442)	198
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in dollars per share)	$ 1.42
Balance, beginning of period at Mar. 31, 2024		$ 561	1,112	23,456	(5,509)	(7,198)	200
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in accrued stock compensation costs			80
Issuance of shares under stock compensation plans and employee stock purchase plans			5			56
Purchase of non-controlling interest			0
Net income attributable to the Company	$ 1,140			1,125			15
Dividend equivalents declared				(2)
Dividends declared				(1)
Other comprehensive (loss) income, net of tax	(18)				(18)
Purchase of treasury shares						(300)
Net non-controlling interests acquired							0
Distributions and other changes							(17)
Balance, end of period at Jun. 30, 2024	$ 13,565		$ 1,197	$ 24,578	$ (5,527)	$ (7,442)	$ 198
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in dollars per share)	$ 0

Nature of Operations

Nature of Operations	6 Months Ended
	Jun. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	Nature of Operations Marsh & McLennan Companies, Inc., and its consolidated subsidiaries (the "Company"), a global professional services firm, is organized based on the different services that it offers. Under this structure, the Company’s two business segments are Risk and Insurance Services and Consulting. The Risk and Insurance Services segment ("RIS") includes risk management activities (risk advice, risk transfer, and risk control and mitigation solutions) as well as insurance and reinsurance broking and services for businesses, public entities, insurance companies, associations, professional services organizations, and private clients. The Company conducts business in this segment through Marsh and Guy Carpenter. Marsh provides data-driven risk advisory services and insurance solutions to commercial and consumer clients. Guy Carpenter develops advanced risk, reinsurance and capital strategies that help clients grow profitably and pursue emerging opportunities.

Principles of Consolidation and

Principles of Consolidation and Other Matters	6 Months Ended
	Jun. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Principles of Consolidation and Other Matters	Principles of Consolidation and Other Matters The Company prepared the consolidated financial statements included herein pursuant to the rules and regulations of the Securities and Exchange Commission. For interim filings, certain information and disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (U.S.) have been omitted pursuant to such rules and regulations. The Company believes that the information and disclosures presented are adequate to make such information and disclosures not misleading. These consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023 (the "2023 Form 10-K"). The accompanied consolidated financial statements include all wholly-owned and majority owned subsidiaries. All significant inter-company transactions and balances have been eliminated. The financial information contained herein reflects all normal recurring adjustments which are, in the opinion of management, necessary for a fair presentation of the Company’s consolidated financial statements as of and for the six months ended June 30, 2024 and 2023. The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. On an ongoing basis, the Company evaluates its estimates, judgments and methodologies. The estimates are based on historical experience and on various other assumptions that the Company believes are reasonable. Such matters include: • estimates of revenue; • impairment assessments and charges; • recoverability of long-lived assets; • liabilities for errors and omissions; • deferred tax assets, uncertain tax positions and income tax expense; • share-based and incentive compensation expense; • the allowance for current expected credit losses on receivables; • useful lives assigned to long-lived assets, and depreciation and amortization; and • fair value estimates of contingent consideration receivable or payable related to acquisitions or dispositions. The Company believes these estimates are reasonable based on information currently available at the time they are made. The Company also considered the potential impact of macroeconomic factors including from the multiple major wars, escalating conflict throughout the Middle East and rising tension in the South China Sea, slower GDP growth or recession, lower interest rates, capital markets volatility, inflation and changes in insurance premium rates to its customer base in various industries and geographies. Insurance exposures subject to variable factors are subject to mid-term and end-of-term adjustments, as well as policy audits, which may reduce premiums and corresponding commissions. Estimates were updated based on internal and industry specific economic data. Actual results may differ from these estimates. Cash and Cash Equivalents Cash and cash equivalents primarily consist of certificates of deposit and time deposits, with original maturities of three months or less, and money market funds. The estimated fair value of the Company's cash and cash equivalents approximates their carrying value. The Company is required to maintain operating funds primarily related to regulatory requirements outside of the U.S. or as collateral under captive insurance arrangements. At June 30, 2024, the Company maintained $505 million compared to $486 million at December 31, 2023 related to these regulatory requirements. Allowance for Credit Losses on Accounts Receivable The Company’s policy for providing an allowance for credit losses on its accounts receivable is based on a combination of factors, including historical write-offs, aging of balances, and other qualitative and quantitative analyses. The charge related to expected credit losses was not material to the consolidated statements of income for the three and six months ended June 30, 2024 and 2023, respectively. Investments The caption "Investment income" in the consolidated statements of income comprises realized and unrealized gains and losses from investments recognized in earnings. It includes, when applicable, other than temporary declines in the value of securities, mark-to-market increases or decreases in equity investments with readily determinable fair values and equity method gains or losses on the Company's investments in private equity funds. The Company holds investments in certain private equity funds. Investments in private equity funds are accounted for in accordance with the equity method of accounting using a consistently applied three-month lag period adjusted for any known significant changes from the lag period to the reporting date of the Company. The underlying private equity funds follow investment company accounting, where investments within the fund are carried at fair value. Investment gains or losses for its proportionate share of the change in fair value of the funds are recorded in earnings. Investments accounted for in accordance with the equity method of accounting are included in other assets in the consolidated balance sheets. The Company recorded net investment income of $1 million and $2 million for the three and six months ended June 30, 2024, respectively, compared to net investment income of $3 million and $5 million, respectively, for the corresponding periods in the prior year. Income Taxes The Company's effective tax rate for the three months ended June 30, 2024 was 27.1%, compared with 24.4% for the corresponding quarter of 2023. The effective tax rates for the six months ended June 30, 2024 and 2023 were 25.4% and 24.6%, respectively. The tax rate in each period reflects the impact of discrete tax items such as excess tax benefits related to share-based compensation, enacted tax legislation, changes in uncertain tax positions, deferred tax adjustments, non-taxable adjustments related to contingent consideration for acquisitions, and valuation allowances for certain tax credits and attributes. The rate for the three and six months ended June 30, 2024 reflects the previously enacted change in the United Kingdom (U.K.) corporate income tax rate from 19% to 25%, which was effective April 1, 2023. The blended U.K. statutory tax rate for 2023 was 23.5%. The excess tax benefit related to share-based payments is the most significant discrete item in both periods, reducing the effective tax rate by 0.7% and 1.2% for the three months ended June 30, 2024 and 2023, respectively, and by 1.6% and 1.3% for the six months periods ended June 30, 2024 and 2023, respectively. The Company's tax rate reflects its income, statutory tax rates, and tax planning in the various jurisdictions in which it operates. Significant judgment is required in determining the annual effective tax rate and in evaluating uncertain tax positions. Losses in one jurisdiction, generally, cannot offset earnings in another, and within certain jurisdictions profits and losses may not offset between entities. Consequently, losses in certain jurisdictions may require valuation allowances affecting the effective tax rate, depending on estimates of the realizability of associated deferred tax assets. The tax rate is also sensitive to changes in unrecognized tax benefits, including the impact of settled tax audits and expired statutes of limitations. The Company reports a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in tax returns. The Company's gross unrecognized tax benefits were $119 million at June 30, 2024, and $124 million at December 31, 2023. It is reasonably possible that the total amount of unrecognized tax benefits could decrease up to approximately $66 million within the next twelve months due to settlement of audits and expirations of statutes of limitations. Changes in tax laws, rulings, policies, or related legal and regulatory interpretations occur frequently and may have significant favorable or adverse impacts on our effective tax rate. In 2021, the Organization for Economic Cooperation and Development ("OECD") released model rules for a 15% global minimum tax, known as Pillar Two. Pillar Two has now been enacted by approximately 35 countries, including the U.K. and Ireland. This minimum tax is treated as a period cost beginning in 2024 and does not have a material impact on the Company's financial results of operations for the current period. The Company is monitoring legislative developments, as well as additional guidance from countries that have enacted legislation. We anticipate further legislative activity and administrative guidance in 2024. Restructuring Costs Charges associated with restructuring activities are recognized in accordance with applicable accounting guidance which includes accounting for disposal or exit activities, guidance related to impairment of right-of-use ("ROU") assets related to real estate leases, as well as other costs resulting from accelerated depreciation or amortization of leasehold improvements and other property and equipment. Severance and related costs are recognized based on amounts due under established severance plans or estimates of one-time benefits that will be provided. Typically, severance benefits are recognized when the impacted colleagues are notified of their expected termination and such termination is expected to occur within the legally required notification period. These costs are included in compensation and benefits in the consolidated statements of income. Costs for real estate consolidation are recognized based on the type of cost, and the expected future use of the facility. For locations where the Company does not expect to sub-lease the property, the amortization of any ROU asset is accelerated from the decision date to the cease use date. For locations where the Company expects to sub-lease the properties subsequent to its vacating the property, the ROU asset is reviewed for potential impairment at the earlier of the cease use date or the date a sub-lease is signed. To determine the amount of impairment, the fair value of the ROU asset is determined based on the present value of the estimated net cash flows related to the property. Contractual costs outside of the ROU asset are recognized based on the net present value of expected future cash outflows for which the Company will not receive any benefit. Such amounts are reliant on estimates of future sub-lease income to be received and future contractual costs to be incurred. These costs are included in other operating expenses in the consolidated statements of income. Other costs related to restructuring, such as moving, legal or consulting costs are recognized as incurred. These costs are included in other operating expenses in the consolidated statements of income. Foreign Currency

Revenue

Revenue	6 Months Ended
	Jun. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue	Revenue The core principle of the revenue recognition guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this principle, the entity applies the following steps: identify the contract(s) with the customer, identify the performance obligations in the contract(s), determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when (or as) the entity satisfies a performance obligation. In accordance with the accounting guidance, a performance obligation is satisfied either at a "point in time" or "over time", depending on the nature of the product or service provided, and the specific terms of the contract with customers. Other revenue included in the consolidated statements of income that is not from contracts with customers is less than 1% of total revenue and is not presented as a separate line item. The Company's revenue policies are provided in more detail in Note 2, Revenue, in the 2023 Form 10-K. The following table disaggregates various components of the Company's revenue: Three Months Ended Six Months Ended (In millions) 2024 2023 2024 2023 Marsh: EMEA $ 912 $ 858 $ 1,937 $ 1,790 Asia Pacific 391 357 727 669 Latin America 137 137 262 252 Total International 1,440 1,352 2,926 2,711 U.S./Canada 1,825 1,686 3,342 3,071 Total Marsh 3,265 3,038 6,268 5,782 Guy Carpenter 632 576 1,780 1,647 Subtotal 3,897 3,614 8,048 7,429 Fiduciary interest income 125 108 247 199 Total Risk and Insurance Services $ 4,022 $ 3,722 $ 8,295 $ 7,628 Mercer: Wealth $ 612 $ 637 $ 1,284 $ 1,218 Health 547 518 1,085 1,063 Career 220 219 435 437 Total Mercer 1,379 1,374 2,804 2,718 Oliver Wyman Group 837 798 1,626 1,485 Total Consulting $ 2,216 $ 2,172 $ 4,430 $ 4,203 The following table provides contract assets and contract liabilities information from contracts with customers: (In millions) June 30, 2024 December 31, 2023 Contract assets $ 430 $ 357 Contract liabilities $ 885 $ 869 The Company records accounts receivable when the right to consideration is unconditional, subject only to the passage of time. Contract assets primarily relate to quota share reinsurance brokerage and contingent insurer revenue. The Company does not have the right to bill and collect revenue for quota share brokerage until the underlying policies written by the ceding insurer attach to the treaty. Estimated revenue related to the achievement of volume or loss ratio metrics cannot be billed or collected until all related policy placements are completed and the contingency is resolved. Contract assets are included in other current assets in the Company's consolidated balance sheets. Contract liabilities primarily relate to the advance consideration received from customers. Contract liabilities are included in current liabilities in the Company's consolidated balance sheets. Revenue recognized for the three and six months ended June 30, 2024 that was included in the contract liability balance at the beginning of each of those periods was $266 million and $581 million, respectively, compared to revenue recognized of $218 million and $511 million, respectively, for the corresponding periods in the prior year. The amount of revenue recognized for the three and six months ended June 30, 2024 from performance obligations satisfied in previous periods, mainly due to variable consideration from contracts with insurers, quota share business and consulting contracts previously considered constrained was $29 million and $43 million, respectively, and $27 million and $44 million, respectively, for the corresponding periods in the prior year. The Company applies the practical expedient and does not disclose the value of unsatisfied performance obligations for (1) contracts with original contract terms of one year or less and (2) contracts where the Company has the right to invoice for services performed.

Fiduciary Assets and Liabilitie

Fiduciary Assets and Liabilities	6 Months Ended
	Jun. 30, 2024
Fiduciary Assets And Liabilities [Abstract]
Fiduciary Assets and Liabilities	Fiduciary Assets and Liabilities The Company, in its capacity as an insurance broker or agent, generally collects premiums from insureds and after deducting its commissions, remits the premiums to the respective insurance underwriters. The Company also collects claims or refunds from underwriters on behalf of insureds. Unremitted insurance premiums and claims proceeds are held by the Company in a fiduciary capacity. The Company's fiduciary assets primarily include bank or short-term time deposits and liquid money market funds, classified as cash and cash equivalents. Since cash and cash equivalents held in a fiduciary capacity are not available for corporate use, they are shown separately in the consolidated balance sheets as cash and cash equivalents held in a fiduciary capacity, with a corresponding amount in current liabilities. Risk and Insurance Services revenue includes interest on fiduciary assets of $125 million and $247 million for the three and six months ended June 30, 2024 , respectively, and $108 million and $199 million for the three and six months ended June 30, 2023 , respectively.

Per Share Data

Per Share Data	6 Months Ended
	Jun. 30, 2024
Earnings Per Share [Abstract]
Per Share Data	Per Share Data Basic net income per share attributable to the Company is calculated by dividing the after-tax income attributable to the Company by the weighted average number of outstanding shares of the Company’s common stock. Diluted net income per share attributable to the Company is calculated by dividing the after-tax income attributable to the Company by the weighted average number of outstanding shares of the Company’s common stock, which have been adjusted for the dilutive effect of potentially issuable common shares. Basic and Diluted EPS Calculation Three Months Ended Six Months Ended (In millions, except per share data) 2024 2023 2024 2023 Net income before non-controlling interests $ 1,140 $ 1,047 $ 2,564 $ 2,299 Less: Net income attributable to non-controlling interests 15 12 39 29 Net income attributable to the Company $ 1,125 $ 1,035 $ 2,525 $ 2,270 Basic weighted average common shares outstanding 492 495 492 495 Dilutive effect of potentially issuable common shares 4 4 5 4 Diluted weighted average common shares outstanding 496 499 497 499 Average stock price used to calculate common stock equivalents $ 205.67 $ 177.33 $ 202.53 $ 172.13

Supplemental Disclosures to the

Supplemental Disclosures to the Consolidated Statements of Cash Flows	6 Months Ended
	Jun. 30, 2024
Supplemental Cash Flow Information [Abstract]
Supplemental Disclosures to the Consolidated Statements of Cash Flows	Supplemental Disclosures to the Consolidated Statements of Cash Flows The following table provides additional information concerning acquisitions, interest and income taxes paid for the six months ended June 30, 2024 and 2023: (In millions) 2024 2023 Assets acquired, excluding cash, cash equivalents, and cash and cash equivalents held in a fiduciary capacity $ 721 $ 364 Fiduciary liabilities assumed (5) (1) Liabilities assumed (18) (63) Contingent/deferred purchase consideration (54) (8) Net cash outflow for acquisitions $ 644 $ 292 (In millions) 2024 2023 Interest paid $ 295 $ 245 Income taxes paid, net of refunds $ 658 $ 504 The classification of contingent consideration in the consolidated statements of cash flows is dependent upon whether the receipt or payment was part of the initial liability established on the acquisition date (financing) or an adjustment to the acquisition date liability (operating). The following amounts are included in the consolidated statements of cash flows as operating and financing activities: For the Six Months Ended June 30, (In millions) 2024 2023 Operating: Contingent consideration payments for prior year acquisitions $ (90) $ (41) Receipt of contingent consideration for dispositions — 1 Acquisition/disposition related net charges for adjustments 15 17 Adjustments and payments related to contingent consideration $ (75) $ (23) Financing: Contingent consideration for prior year acquisitions $ (71) $ (134) Deferred consideration related to prior year acquisitions (10) (51) Payments of deferred and contingent consideration for acquisitions $ (81) $ (185) Receipts of contingent consideration for dispositions $ 1 $ 2 The Company had non-cash issuances of common stock in accordance with its share-based payment plan of $321 million and $296 million for the six months ended June 30, 2024 and 2023, respectively. The Company recorded share-based compensation expense related to restricted stock units, performance stock units and stock options of $90 million and $193 million for the three and six months ended June 30, 2024, respectively, and $92 million and $191 million for the three and six months ended June 30, 2023, respectively.

Other Comprehensive (Loss) Inco

Other Comprehensive (Loss) Income	6 Months Ended
	Jun. 30, 2024
Equity [Abstract]
Other Comprehensive (Loss) Income	Other Comprehensive (Loss) Income The changes, net of tax, in the balances of each component of AOCI for the three and six months ended June 30, 2024 and 2023, including amounts reclassified out of AOCI, are as follows: (In millions) Pension/Post-Retirement Plans Gains (Losses) Foreign Currency Translation Adjustments Total Balance at April 1, 2024 $ (3,064) $ (2,445) $ (5,509) Other comprehensive income (loss) before reclassifications 9 (32) (23) Amounts reclassified from accumulated other comprehensive income 5 — 5 Net current period other comprehensive income (loss) 14 (32) (18) Balance at June 30, 2024 (a) $ (3,050) $ (2,477) $ (5,527) (In millions) Pension/Post-Retirement Plans Gains (Losses) Foreign Currency Translation Adjustments Total Balance at April 1, 2023 $ (2,766) $ (2,468) $ (5,234) Other comprehensive (loss) income before reclassifications (48) 224 176 Amounts reclassified from accumulated other comprehensive income 3 — 3 Net current period other comprehensive (loss) income (45) 224 179 Balance at June 30, 2023 (a) $ (2,811) $ (2,244) $ (5,055) (a) At June 30, 2024 and 2023, balances are net of deferred tax assets in pension and post-retirement plans gains (losses) of $1.5 billion and $1.4 billion, respectively. (In millions) Pension/Post-Retirement Plans Gains (Losses) Foreign Currency Translation Adjustments Total Balance at January 1, 2024 $ (3,101) $ (2,194) $ (5,295) Other comprehensive income (loss) before reclassifications 42 (283) (241) Amounts reclassified from accumulated other comprehensive income 9 — 9 Net current period other comprehensive income (loss) 51 (283) (232) Balance at June 30, 2024 (a) $ (3,050) $ (2,477) $ (5,527) (In millions) Pension/Post-Retirement Plans Gains (Losses) Foreign Currency Translation Adjustments Total Balance at January 1, 2023 $ (2,721) $ (2,593) $ (5,314) Other comprehensive (loss) income before reclassifications (96) 349 253 Amounts reclassified from accumulated other comprehensive income 6 — 6 Net current period other comprehensive (loss) income (90) 349 259 Balance at June 30, 2023 (a) $ (2,811) $ (2,244) $ (5,055) (a) At June 30, 2024 and 2023, balances are net of deferred tax assets in pension and post-retirement plans gains (losses) of $1.5 billion and $1.4 billion, respectively. The components of other comprehensive (loss) income for the three and six months ended June 30, 2024 and 2023 are as follows: Three Months Ended June 30, 2024 2023 (In millions) Pre-Tax Tax Net of Tax Pre-Tax Tax (Credit) Net of Tax Foreign currency translation adjustments $ (28) $ 4 $ (32) $ 223 $ (1) $ 224 Pension/post-retirement plans: Amortization of (gains) losses included in net benefit (credit) cost: Prior service credits (a) (1) — (1) (1) — (1) Net actuarial losses (a) 7 1 6 5 1 4 Subtotal 6 1 5 4 1 3 Foreign currency translation adjustments 12 3 9 (59) (16) (43) Other adjustments — — — (7) (2) (5) Pension/post-retirement plans gains (losses) 18 4 14 (62) (17) (45) Other comprehensive (loss) income $ (10) $ 8 $ (18) $ 161 $ (18) $ 179 (a) Included in other net benefit credits in the consolidated statements of income. Income tax expense on net actuarial losses are included in income tax expense. Six Months Ended June 30, 2024 2023 (In millions) Pre-Tax Tax Net of Tax Pre-Tax Tax (Credit) Net of Tax Foreign currency translation adjustments $ (272) $ 11 $ (283) $ 342 $ (7) $ 349 Pension/post-retirement plans: Amortization of (gains) losses included in net benefit (credit) cost: Prior service credits (a) (1) — (1) (1) — (1) Net actuarial losses (a) 13 3 10 10 3 7 Subtotal 12 3 9 9 3 6 Foreign currency translation adjustments 56 14 42 (122) (31) (91) Other adjustments — — — (7) (2) (5) Pension/post-retirement plans gains (losses) 68 17 51 (120) (30) (90) Other comprehensive (loss) income $ (204) $ 28 $ (232) $ 222 $ (37) $ 259 (a) Included in other net benefit credits in the consolidated statements of income. Income tax expense on net actuarial losses are included in income tax expense.

Acquisitions and Dispositions

Acquisitions and Dispositions	6 Months Ended
	Jun. 30, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Acquisitions and Dispositions	Acquisitions and Dispositions The Company’s acquisitions have been accounted for as business combinations. Net assets and results of operations are included in the Company’s consolidated financial statements commencing at the respective purchase closing dates. In connection with acquisitions, the Company records the estimated values of the net tangible assets and the identifiable intangible assets purchased, which typically consist of customer relationships, developed technology, trademarks and non-compete agreements. The valuation of purchased intangible assets involves significant estimates and assumptions. The Company estimates the fair value of purchased intangible assets, primarily using the income approach, by determining the present value of future cash flows over the remaining economic life of the respective assets. The significant estimates and assumptions used in this approach include the determination of the discount rate, economic life, future revenue growth rates, expected account attrition rates and earnings margins. Refinement and completion of final valuation of net assets acquired could affect the carrying value of tangible assets, goodwill and identifiable intangible assets. The Risk and Insurance Services segment completed 5 acquisitions for the six months ended June 30, 2024: • January – Marsh acquired NOSCO Insurance Service Company Ltd., a Japan-based insurance broker that provides affinity type schemes, corporate and personal lines insurance. • March – Marsh & McLennan Agency ("MMA") acquired Louisiana-based insurance brokers, Querbes & Nelson ("Q&N") and Louisiana Companies. Q&N offers business insurance, employee benefits, and alternative risk financing consulting to a variety of businesses with specific expertise in energy services, commercial contractors, and transportation. Louisiana Companies provides business and personal lines insurance to businesses and individuals with specific expertise in the construction, manufacturing, distributor, healthcare, and hospitality industries. • May – MMA acquired AC Risk Management, a New York-based commercial lines insurance broker primarily offering property and casualty insurance to businesses with a focus on the construction industry; Perkins Insurance Agencies LLC, a Texas-based insurance broker providing commercial property and casualty and personal lines coverage to businesses, non-profits and families with expertise in the oil and gas, trucking, farm and ranch and restaurant industries; and Fisher Brown Bottrell Insurance, Inc., a Mississippi-based insurance broker providing commercial property and casualty insurance, surety and employee benefits services to businesses and individuals. The Consulting segment completed 4 acquisitions for the six months ended June 30, 2024: • February – Oliver Wyman Group acquired SeaTec Consulting Inc., a Georgia-based firm that provides consulting, engineering, and digital expertise across the aviation, aerospace and defense, and transportation industries. • March – Mercer acquired Vanguard's Institutional Advisory Services business unit ("Vanguard"), a Pennsylvania-based outsourced chief investment officer ("OCIO") business, that provides investment management services for not-for-profit organizations and other institutional investors in the U.S. Mercer also acquired The Talent Enterprise, a United Arab Emirates-based psychometric and talent assessment technology company, that provides talent assessment tools and talent capability development solutions. Oliver Wyman Group acquired Innopay NL B.V., a Netherlands-based consultancy firm that delivers strategy, scheme development, and execution in the domain of digital payments, open finance, digital identity and data sharing. Total purchase consideration for acquisitions made for the six months ended June 30, 2024 was $716 million, which consisted of cash paid of $662 million and deferred and estimated contingent purchase consideration of $54 million. Contingent purchase consideration arrangements are generally based on earnings before interest, tax, depreciation and amortization ("EBITDA") or revenue targets over a period of 2 to 4 years. The fair value of contingent purchase consideration was based on projected revenue and earnings of the acquired entities. For the six months ended June 30, 2024, the Company also paid $10 million of deferred purchase consideration and $161 million of contingent purchase consideration related to prior year acquisitions. Estimated fair values of assets acquired and liabilities assumed are subject to adjustment until purchase accounting is finalized. The following table presents the preliminary allocation of purchase consideration to the assets acquired and liabilities assumed in 2024, based on the estimated fair values for the acquisitions as of their respective acquisition dates. Amounts in the table primarily reflect the impact of the Fisher Brown Bottrell Insurance, Inc. and Vanguard acquisitions. Acquisitions through June 30, 2024 (In millions) Cash $ 662 Estimated fair value of deferred/contingent purchase consideration 54 Total consideration $ 716 Allocation of purchase price: Cash and cash equivalents $ 13 Cash and cash equivalents held in a fiduciary capacity 5 Net receivables 49 Other current assets 22 Goodwill 430 Other intangible assets 215 Fixed assets, net 3 Other assets 2 Total assets acquired 739 Current liabilities 9 Fiduciary liabilities 5 Other liabilities 9 Total liabilities assumed 23 Net assets acquired $ 716 The purchase price allocation for assets acquired and liabilities assumed is based on estimates that are preliminary in nature and subject to adjustments, which could be material. Any necessary adjustments must be finalized during the measurement period, which for a particular asset, liability, or non-controlling interest ends once the acquirer determines that either (1) the necessary information has been obtained or (2) the information is not available. However, the measurement period for all items is limited to one year from the acquisition date. Items subject to change include: • amounts of intangible assets, fixed assets, capitalized software assets and right-of-use assets, subject to finalization of valuation efforts; • amounts for contingencies, pending the finalization of the Company’s assessment of the portfolio of contingencies; • amounts for deferred tax assets and liabilities, pending the finalization of valuations of the assets acquired, liabilities assumed and associated goodwill; and • amounts for income tax assets, receivables and liabilities, pending the filing of the acquired companies' pre-acquisition income tax returns and receipt of information from taxing authorities which may change certain estimates and assumptions used. The estimation of fair value requires numerous judgments, assumptions and estimates about future events and uncertainties, which could materially impact these values, and the related amortization, where applicable, in the Company’s results of operations. The following table provides information about other intangible assets acquired in 2024: Other intangible assets through June 30, 2024 (In millions) Amount Weighted Average Amortization Period Client relationships $ 205 11.8 years Other 10 2.8 years Total other intangible assets $ 215 The consolidated statements of income include the results of operations of acquired companies since their respective acquisition dates. The consolidated statements of income for the three and six months ended June 30, 2024 include revenue of approximately $48 million and $62 million, respectively, and operating income of $3 million and operating loss of $3 million, respectively, for acquisitions made in 2024. The consolidated statements of income for both the three and six months ended June 30, 2023 include revenue of approximately $41 million and operating income of $9 million for acquisitions made in 2023. The Company incurred approximately $21 million and $29 million of acquisition related expenses for the three and six months ended June 30, 2024, respectively. For the three and six months ended June 30, 2023, the Company incurred integration costs of $10 million and $27 million, respectively, for the acquisition of Westpac Banking Corporation's ("Westpac") financial advisory business, Advance Asset Management, and the transfer from Westpac of BT Financial Group's personal corporate pension funds to the Mercer Super Trust managed by Mercer Australia (referred to collectively, as the "Westpac Transaction"). These expenses related primarily to technology, consulting, legal and people related costs. Acquisition and integration costs are included in other operating expenses in the Company's consolidated statements of income. Dispositions On January 1, 2024, the Company sold its Mercer U.K. pension administration and U.S. health and benefits administration businesses for approximately $114 million and recorded a net gain of $21 million, which is included in revenue in the consolidated statements of income. As part of the disposition of the businesses, the Company incurred exit costs of $18 million in the first quarter of 2024. These costs are included in expenses in the Company's consolidated statements of income. Prior year acquisitions The Risk and Insurance Services segment completed 9 acquisitions in 2023: • May – Marsh acquired Austral Insurance Brokers Pty Ltd, an Australia-based insurance broker that provides risk advice services and business insurance solutions in the labor hire, mining services, transport, manufacturing, agribusiness, retail and professional services sectors. • June – Guy Carpenter acquired Re Solutions, an Israel-based reinsurance broker with actuarial and analytics capabilities and solutions, including an extensive facultative reinsurance offering, and MMA acquired SOLV Risk Solutions, LLC, a Texas-based risk management advisory services firm. • July – MMA acquired Integrity HR, Inc., a Kentucky-based human resources consulting firm and Trideo Systems, an Illinois-based risk management information systems provider for health care organizations, and Marsh acquired Asprose Corredora de Seguros, a Costa Rica-based insurance broker that provides insurance brokerage and risk advisory services to commercial organizations. • August – MMA acquired Graham Company, a Pennsylvania-based risk management consultancy and insurance and employee benefits broker, specializing in construction, real estate, manufacturing and distribution, health and human services and professional services. • September – MMA acquired Blue Water Insurance LLC, a Kentucky-based employee health and benefits insurance broker. • November – Marsh acquired HIG Australia Holdco Pty Ltd ("Honan Insurance Group"), an Australia-based insurance broker in the areas of corporate risk, employee benefits, and strata and real estate insurance. The Consulting segment completed 5 acquisitions in 2023: • March – Mercer acquired Leapgen LLC, a Minnesota-based human resources consulting technology advisory firm focused on digital strategy and transformation, workforce solutions, and improving employee experience. • April – Mercer acquired Westpac Banking Corporation’s ("Westpac") financial advisory business, Advance Asset Management, and completed the transfer from Westpac of BT Financial Group's personal and corporate pension funds to the Mercer Super Trust managed by Mercer Australia (referred to collectively, as the "Westpac Transaction"). Oliver Wyman Group acquired the business of Gorman Actuarial, Inc., a Massachusetts-based life and health actuarial consultant business. • July – Oliver Wyman Group acquired the actuarial consulting business of ISC Strategies Consulting, Inc., a Florida-based life insurance and actuarial consulting firm. • October – Mercer acquired BT Financial Group's Private Portfolio Management, an Australia-based wealth management business that provides investment solutions to not-for-profit organizations, high-net worth clients and their financial advisers. Total purchase consideration for acquisitions made for the six months ended June 30, 2023 was $340 million, which consisted of cash paid of $332 million and deferred and estimated contingent purchase consideration of $8 million. Contingent purchase consideration arrangements are generally based primarily on EBITDA or revenue targets over a period of 2 to 4 years. For the first six months of 2023, the Company also paid $51 million of deferred purchase consideration and $175 million of contingent purchase consideration related to acquisitions made in prior years. Estimated fair values of assets acquired and liabilities assumed are subject to adjustment when purchase accounting is finalized. Prior year dispositions In January 2023, the Company entered into an agreement for the sale of an individual financial advisory business in Canada which was completed in May 2023. As a result, the Company recorded a loss of $17 million for the six months ended June 30, 2023, primarily related to the write-down of the customer relationship intangible assets. The loss is included in revenue in the consolidated statements of income. In connection with the disposition of the Mercer U.S. affinity business in 2022, the Company transferred to the buyer an additional $20 million of cash and cash equivalents held in a fiduciary capacity in the first quarter of 2023. Purchase of remaining non-controlling interest In the second quarter of 2023, the Company purchased the remaining interest in a subsidiary for $139 million. Pro-Forma Information The following unaudited pro-forma financial data gives effect to the acquisitions made by the Company in 2024 and 2023. In accordance with accounting guidance related to pro-forma disclosures, the information presented for acquisitions made in 2024 is as if they occurred on January 1, 2023, and reflects acquisitions made in 2023, as if they occurred on January 1, 2022. The unaudited pro-forma information includes the effects of amortization of acquired intangibles in all years. The unaudited pro-forma financial data is presented for illustrative purposes only and is not necessarily indicative of the operating results that would have been achieved if such acquisitions had occurred on the dates indicated, nor is it necessarily indicative of future consolidated results. Three Months Ended Six Months Ended (In millions, except per share data) 2024 2023 2024 2023 Revenue $ 6,234 $ 5,989 $ 12,756 $ 12,060 Net income attributable to the Company $ 1,135 $ 1,065 $ 2,546 $ 2,317 Basic net income per share attributable to the Company $ 2.31 $ 2.15 $ 5.17 $ 4.68 Diluted net income per share attributable to the Company $ 2.29 $ 2.13 $ 5.13 $ 4.64

Goodwill and Other Intangibles

Goodwill and Other Intangibles	6 Months Ended
	Jun. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Goodwill and Other Intangibles The Company is required to assess goodwill and any indefinite-lived intangible assets for impairment annually, or more frequently if circumstances indicate an impairment may have occurred. The Company performs the annual impairment assessment for each of its reporting units during the third quarter of each year. The reporting unit level is defined as the same level as the Company's operating segments. In accordance with applicable accounting guidance, a company can assess qualitative factors to determine whether it is necessary to perform a quantitative goodwill impairment test. Alternatively, the Company may elect to proceed directly to the quantitative goodwill impairment test. In 2023, the Company performed a quantitative goodwill impairment assessment. Fair values for the reporting units were estimated using both an income and market valuation approach. The carrying values were based on balances at June 30, 2023 and included directly identified assets and liabilities, as well as an allocation of those assets and liabilities not recorded at the reporting unit level. The Company concluded that goodwill was not impaired, as the fair value of each reporting unit exceeded the carrying value. Other intangible assets that are not deemed to have an indefinite life are amortized over their estimated lives and assessed for impairment upon the occurrence of certain triggering events in accordance with applicable accounting literature. Based on its assessment, the Company concluded that other intangible assets were not impaired. The Company had no indefinite lived intangible assets at June 30, 2024 and December 31, 2023. Changes in the carrying amount of goodwill are as follows: (In millions) 2024 2023 Balance at January 1, $ 17,231 $ 16,251 Goodwill acquired 430 236 Other adjustments (a) (145) 134 Balance at June 30, $ 17,516 $ 16,621 (a) Primarily reflects the impact of foreign exchange. The goodwill from acquisitions in 2024 and 2023 consists largely of the synergies and economies of scale expected from combining the operations of the Company and the acquired entities and the trained and assembled workforce acquired. The goodwill acquired in 2024 included approxi mately $254 million and $81 million in t he Risk and Insurance Services and Consulting segments, respectively, which is deductible for tax purposes. Goodwill allocated to the Company’s reportable segments at June 30, 2024 is $13.4 billion for Risk and Insurance Services and $4.1 billion for Consulting. The gross cost and accumulated amortization of other identified intangible assets at June 30, 2024 and December 31, 2023 are as follows: June 30, 2024 December 31, 2023 (In millions) Gross Accumulated Net Gross Accumulated Net Client relationships $ 4,498 $ 1,905 $ 2,593 $ 4,337 $ 1,761 $ 2,576 Other (a) 376 331 45 391 337 54 Other intangible assets $ 4,874 $ 2,236 $ 2,638 $ 4,728 $ 2,098 $ 2,630 (a) Primarily reflects non-compete agreements, trade names and developed technology. Aggregate amortization expense for the three and six months ended June 30, 2024 was $89 million and $179 million, respectively, compared to $87 million and $172 million, respectively, for the corresponding periods in the prior year. The estimated future aggregate amortization expense is as follows: For the Years Ending December 31, (In millions) Estimated Expense 2024 (excludes amortization through June 30, 2024) $ 174 2025 322 2026 301 2027 293 2028 271 Subsequent years 1,277 Total future amortization $ 2,638

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair Value Hierarchy The Company has categorized its assets and liabilities that are valued at fair value on a recurring basis into a three-level fair value hierarchy. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets and liabilities (Level 1) and lowest priority to unobservable inputs (Level 3). In some cases, the inputs used to measure fair value might fall into different levels of the fair value hierarchy. In such cases, the level in the fair value hierarchy, for disclosure purposes, is determined based on the lowest level input that is significant to the fair value measurement. Assets and liabilities recorded in the consolidated balance sheets at fair value are categorized based on the inputs in the valuation techniques as follows: Level 1. Assets and liabilities whose values are based on unadjusted quoted prices for identical assets or liabilities in an active market (examples include active exchange-traded equity securities and exchange-traded money market mutual funds). Assets and liabilities measured using Level 1 inputs include exchange-traded equity securities, exchange-traded mutual funds and money market funds. Level 2. Assets and liabilities whose values are based on the following: a) quoted prices for similar assets or liabilities in active markets; b) quoted prices for identical or similar assets or liabilities in non-active markets (examples include corporate and municipal bonds, which trade infrequently); c) pricing models whose inputs are observable for substantially the full term of the asset or liability (examples include most over-the-counter derivatives, including interest rate and currency swaps); and d) pricing models whose inputs are derived principally from or corroborated by observable market data through correlation or other means for substantially the full asset or liability (for example, certain mortgage loans). Level 3. Assets and liabilities whose values are based on prices, or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs reflect management’s own assumptions about the assumptions a market participant would use in pricing the asset or liability. Assets and liabilities measured using Level 3 inputs relate to assets and liabilities for contingent purchase consideration. Valuation Techniques Equity Securities, Money Market Funds and Mutual Funds – Level 1 Investments for which market quotations are readily available are valued at the sale price on their principal exchange or, for certain markets, official closing bid price. Money market funds are valued at a readily determinable price. Contingent Purchase Consideration Assets and Liabilities – Level 3 Purchase consideration for some acquisitions and dispositions made by the Company include contingent consideration arrangements. Contingent consideration arrangements are based primarily on EBITDA or revenue targets over a period of 2 to 4 years. The fair value of the contingent purchase consideration asset and liability is estimated as the present value of future cash flows to be paid, based on projections of revenue and earnings and related targets of the acquired and disposed entities. The following fair value hierarchy table presents information about the Company’s assets and liabilities measured at fair value on a recurring basis at June 30, 2024 and December 31, 2023: Identical Assets Observable Inputs Unobservable Inputs Total (In millions) 06/30/24 12/31/23 06/30/24 12/31/23 06/30/24 12/31/23 06/30/24 12/31/23 Assets: Financial instruments owned: Exchange traded equity securities (a) $ 8 $ 5 $ — $ — $ — $ — $ 8 $ 5 Mutual funds (a) 182 178 — — — — 182 178 Money market funds (b) 354 606 — — — — 354 606 Contingent purchase consideration assets (c) — — — — — 1 — 1 Total assets measured at fair value $ 544 $ 789 $ — $ — $ — $ 1 $ 544 $ 790 Fiduciary Assets: Money market funds $ 65 $ 180 $ — $ — $ — $ — $ 65 $ 180 Total fiduciary assets measured $ 65 $ 180 $ — $ — $ — $ — $ 65 $ 180 Liabilities: Contingent purchase consideration liabilities (d) $ — $ — $ — $ — $ 121 $ 252 $ 121 $ 252 Total liabilities measured at fair value $ — $ — $ — $ — $ 121 $ 252 $ 121 $ 252 (a) Included in other assets in the consolidated balance sheets. (b) Included in cash and cash equivalents in the consolidated balance sheets. (c) Included in other receivables in the consolidated balance sheets. (d) Included in accounts payable and accrued liabilities and other liabilities in the consolidated balance sheets. The Level 3 assets in the table reflect contingent purchase consideration from the sale of businesses. During the six months ended June 30, 2024 and 2023, there were no assets or liabilities that were transferred between levels. The change in the contingent purchase consideration assets from December 31, 2023 is driven primarily by cash receipts of approximately $1 million. The following table sets forth a summary of the changes in fair value of the Company’s Level 3 liabilities for the three and six months ended June 30, 2024 and 2023: Three Months Ended Six Months Ended (In millions) 2024 2023 2024 2023 Balance at beginning of period $ 242 $ 383 $ 252 $ 377 Net additions 4 4 17 4 Payments (135) (174) (161) (175) Revaluation impact 9 10 15 17 Other 1 — (2) — Balance at end of period $ 121 $ 223 $ 121 $ 223 Long-Term Investments The Company has investments in public and private companies as well as certain private equity investments that are accounted for using the equity method of accounting. The carrying value of these investments was $276 million and $266 million at June 30, 2024 and December 31, 2023, respectively. Investments in Public and Private Companies The Company has investments in private insurance and consulting companies with a carrying value of $73 million and $63 million at June 30, 2024 and December 31, 2023, respectively. These investments are accounted for using the equity method of accounting, the results of which are included in revenue in the consolidated statements of income and the carrying value of which is included in other assets in the consolidated balance sheets. The Company records its share of income or loss on its equity method investments, some of which are on a one quarter lag basis. Private Equity Investments The Company's investments in private equity funds were $203 million at both June 30, 2024 and December 31, 2023. The carrying values of these private equity investments approximate fair value. The underlying private equity funds follow investment company accounting, where investments within the fund are carried at fair value. The Company records in earnings its proportionate share of the change in fair value of the funds on the investment income line in the consolidated statements of income. These investments are included in other assets in the consolidated balance sheets. The Company recorded net investment gains of $1 million for the three months ended June 30, 2024. For the three and six months ended June 30, 2023, the Company recorded net investment gains of $3 million and $6 million, respectively. At June 30, 2024, the Company has commitments of potential future investments of approximately $114 million in private equity funds that invest primarily in financial services companies. Other Investments The Company held equity investments with readily determinable market values at June 30, 2024 and December 31, 2023, of $19 million and $16 million, respectively. For the six months ended June 30, 2024, the Company recorded mark-to-market investment gains on these investments of $2 million. For the six months ended June 30, 2023, the Company recorded mark-to-market losses on these investments of $1 million.

Derivatives

Derivatives	6 Months Ended
	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives Net Investment Hedge The Company has investments in various subsidiaries with Euro functional currencies. As a result, the Company is exposed to the risk of fluctuations between the Euro and U.S. dollar exchange rates. The Company designated its €1.1 billion senior note debt instruments ("Euro notes") as a net investment hedge (the "hedge") of its Euro denominated subsidiaries. The hedge effectiveness is re-assessed each quarter to confirm that the designated equity balance at the beginning of each period continues to equal or exceed 80% of the outstanding balance of the Euro debt instrument and that all the critical terms of the hedging instrument and the hedged net investment continue to match. If the hedge is highly effective, the change in the debt balance related to foreign exchange fluctuations is recorded in accumulated other comprehensive loss in the consolidated balance sheets.

Leases

Leases	6 Months Ended
	Jun. 30, 2024
Leases [Abstract]
Leases	Leases The Company leases office facilities under non-cancelable operating leases with terms generally ranging between 10 and 25 years. The Company utilizes these leased office facilities for use by its employees in countries in which the Company conducts its business. The Company’s leases have no restrictions on the payment of dividends, the acquisition of debt or additional lease obligations, or entering into additional lease obligations. The leases also do not contain significant purchase options. Operating leases are recognized on the consolidated balance sheets as ROU assets and operating lease liabilities based on the present value of the remaining future minimum payments over the lease term at commencement date of the lease. For the three and six months ended June 30, 2024 and 2023, the Company determined that $1 million and $2 million, respectively, and $5 million and $13 million, respectively, of the ROU assets were impaired and recorded a charge to the consolidated statements of income with an offsetting reduction to ROU assets. The following table provides additional information about the Company’s property leases: Three Months Ended Six Months Ended (In millions) 2024 2023 2024 2023 Lease Cost: Operating lease cost (a) $ 81 $ 81 $ 163 $ 161 Short-term lease cost 2 2 3 3 Variable lease cost 28 26 54 63 Sublease income (5) (2) (8) (6) Net lease cost $ 106 $ 107 $ 212 $ 221 Other information: Operating cash outflows from operating leases $ 183 $ 189 Right of use assets obtained in exchange for new operating lease liabilities $ 85 $ 121 Weighted average remaining lease term – real estate 7.8 years 8.3 years Weighted average discount rate – real estate leases 3.58 % 3.21 % (a) Excludes ROU asset impairment charges. Future minimum lease payments for the Company’s operating leases at June 30, 2024 are as follows: (In millions) Real Estate Leases 2024 (excludes payments through June 30, 2024) $ 182 2025 355 2026 327 2027 289 2028 214 2029 170 Subsequent years 616 Total future lease payments 2,153 Less: Imputed interest (263) Total $ 1,890 Current lease liabilities $ 304 Long-term lease liabilities 1,586 Total lease liabilities $ 1,890 Note: The above table excludes obligations for leases with original terms of 12 months or less which have not been recognized as a ROU asset or liability in the consolidated balance sheets. At June 30, 2024, the Company had additional operating real estate leases that had not yet commenced of $25 million. These operating leases will commence over the next 12 months .

Retirement Benefits

Retirement Benefits	6 Months Ended
	Jun. 30, 2024
Retirement Benefits [Abstract]
Retirement Benefits	Retirement Benefits The Company maintains qualified and non-qualified defined benefit pension plans for its U.S. and non-U.S. eligible employees. The Company’s policy for funding its tax-qualified defined benefit retirement plans is to contribute amounts at least sufficient to meet the funding requirements set forth by U.S. law and the laws of the non-U.S. jurisdictions in which the Company offers defined benefit plans. The weighted average actuarial assumptions utilized to calculate the net periodic benefit costs for the U.S. and significant non-U.S. defined benefit plans are as follows: Combined U.S. and significant non-U.S. Plans Pension Benefits June 30, 2024 2023 Weighted average assumptions: Expected return on plan assets 5.44 % 5.31 % Discount rate 4.95 % 5.16 % Rate of compensation increase * 3.16 % 3.16 % (*) There are no rate of compensation increase assumptions for the U.S. defined benefit plans since future benefit accruals were discontinued for those plans after December 31, 2016 and earned benefits are not subject to final salary level adjustments. The target asset allocation for the U.S. plans is 50% equities and equity alternatives, and 50% fixed income. At June 30, 2024, the actual allocation for the U.S. plans was 51% equities and equity alternatives, and 49% fixed income. The target allocation for the U.K. plans at June 30, 2024 is 14% equities and equity alternatives, and 86% fixed income. At June 30, 2024, the actual allocation for the U.K. plans was 14% equities and equity alternatives and 86% fixed income. The Company's U.K. plans comprised approximately 79% of non-U.S. plan assets at December 31, 2023. The assets of the Company's defined benefit plans are diversified and are managed in accordance with applicable laws and with the goal of maximizing the plans' real return within acceptable risk parameters. The Company uses threshold-based portfolio re-balancing to ensure the actual portfolio remains consistent with target asset allocation ranges. The net benefit cost or credit of the Company's defined benefit plans is measured on an actuarial basis using various methods and assumptions. The components of the net benefit credit for defined benefit plans are as follows: Combined U.S. and significant non-U.S. Plans For the Three Months Ended June 30, Pension Benefits (In millions) 2024 2023 Service cost $ 6 $ 5 Interest cost 144 150 Expected return on plan assets (216) (215) Amortization of prior service (credit) cost 1 — Recognized actuarial loss 7 5 Net benefit credit $ (58) $ (55) Combined U.S. and significant non-U.S. Plans For the Six Months Ended June 30, Pension Benefits (In millions) 2024 2023 Service cost $ 12 $ 11 Interest cost 288 298 Expected return on plan assets (435) (427) Amortization of prior service (credit) cost 1 — Recognized actuarial loss 15 11 Net benefit credit $ (119) $ (107) The following tables provide the amounts reported in the consolidated statements of income: Combined U.S. and significant non-U.S. Plans For the Three Months Ended June 30, Pension Benefits (In millions) 2024 2023 Compensation and benefits expense $ 6 $ 5 Other net benefit credits (64) (60) Net benefit credit $ (58) $ (55) Combined U.S. and significant non-U.S. Plans For the Six Months Ended June 30, Pension Benefits (In millions) 2024 2023 Compensation and benefits expense $ 12 $ 11 Other net benefit credits (131) (118) Net benefit credit $ (119) $ (107) The components of the net benefit credit for the U.S. defined benefit plans are as follows: U.S. Plans only For the Three Months Ended June 30, Pension Benefits (In millions) 2024 2023 Interest cost $ 63 $ 65 Expected return on plan assets (75) (77) Recognized actuarial loss 5 4 Net benefit credit $ (7) $ (8) U.S. Plans only For the Six Months Ended June 30, Pension Benefits (In millions) 2024 2023 Interest cost $ 125 $ 130 Expected return on plan assets (151) (155) Recognized actuarial loss 10 9 Net benefit credit $ (16) $ (16) The components of the net benefit credit for the non-U.S. defined benefit plans are as follows: Significant non-U.S. Plans only For the Three Months Ended June 30, Pension Benefits (In millions) 2024 2023 Service cost $ 6 $ 5 Interest cost 81 85 Expected return on plan assets (141) (138) Amortization of prior service credit 1 — Recognized actuarial loss 2 1 Net benefit credit $ (51) $ (47) Significant non-U.S. Plans only For the Six Months Ended June 30, Pension Benefits (In millions) 2024 2023 Service cost $ 12 $ 11 Interest cost 163 168 Expected return on plan assets (284) (272) Amortization of prior service credit 1 — Recognized actuarial loss 5 2 Net benefit credit $ (103) $ (91) The Company made contributions to its U.S. and non-U.S. defined benefit pension plans for the three and six months ended June 30, 2024 of approximately $27 million and $51 million, respectively, compared to contributions of $26 million and $47 million, respectively, for the corresponding periods in the prior year. The Company expects to contribute approximately $43 million to its U.S. and non-U.S. defined benefit pension plans during the remainder of 2024. Defined Contribution Plans The Company maintains defined contribution plans ("DC Plans") for its employees, the most significant being in the U.S. and the U.K. The cost of the U.S. DC Plans for the three and six months ended June 30, 2024 was $48 million and $97 million, respectively, and $44 million and $88 million, respectively, for the corresponding periods in the prior year. The cost of the U.K. DC Plans for the three and six months ended June 30, 2024 was $39 million and $91 million, respectively, and $38 million and $81 million, respectively, for the corresponding periods in the prior year.

Debt

Debt	6 Months Ended
	Jun. 30, 2024
Debt Disclosure [Abstract]
Debt	Debt The Company’s outstanding debt is as follows: (In millions) June 30, December 31, 2023 Short-term: Commercial paper $ 749 $ — Current portion of long-term debt 518 1,619 $ 1,267 $ 1,619 Long-term: Senior notes – 3.50% due 2024 $ — $ 600 Senior notes – 3.875% due 2024 — 1,000 Senior notes – 3.50% due 2025 500 499 Senior notes – 1.349% due 2026 593 617 Senior notes – 3.75% due 2026 599 599 Senior notes – 4.375% due 2029 1,499 1,499 Senior notes – 1.979% due 2030 578 601 Senior notes – 2.25% due 2030 742 741 Senior notes – 2.375% due 2031 397 397 Senior notes – 5.750% due 2032 493 493 Senior notes – 5.875% due 2033 298 298 Senior notes – 5.400% due 2033 592 592 Senior notes – 5.150% due 2034 495 — Senior notes – 4.75% due 2039 496 496 Senior notes – 4.35% due 2047 494 494 Senior notes – 4.20% due 2048 593 593 Senior notes – 4.90% due 2049 1,239 1,239 Senior notes – 2.90% due 2051 346 346 Senior notes – 6.25% due 2052 491 491 Senior notes – 5.450% due 2053 591 591 Senior notes – 5.700% due 2053 988 988 Senior notes – 5.450% due 2054 493 — Mortgage – 5.70% due 2035 276 284 Other 3 5 12,796 13,463 Less: current portion 518 1,619 $ 12,278 $ 11,844 The senior notes in the table are registered by the Company with the Securities and Exchange Commission and are not guaranteed. In November 2023, the Company increased its short-term commercial paper financing program (the "Program") to $3.5 billion from $2.8 billion. The Company had previously increased the Program's capacity in October 2022 to $2.8 billion from $2.0 billion. The Company had $749 million of commercial paper outstanding at June 30, 2024, at an average effective interest rate of 5.498%. The Company had no commercial paper outstanding at December 31, 2023. Credit Facilities In October 2023, the Company increased its multi-currency unsecured five-year credit facility (the "Credit Facility") capacity to $3.5 billion from $2.8 billion and extended the expiration to October 2028. The interest rate on the Credit Facility was initially based on LIBOR plus a fixed margin which varied with the Company's credit rating. In the second quarter of 2023, the Credit Facility was amended so that borrowings under the Credit Facility bear interest at a rate per annum, equal, at the Company's option, either at (a) SOFR benchmark rate for U.S. dollar borrowings, or (b) a currency specific benchmark rate, plus an applicable margin which varies with the Company's credit ratings. The Company is required to maintain certain coverage and leverage ratios for the Credit Facility, which are evaluated quarterly. The Credit Facility includes provisions for determining a benchmark replacement rate in the event existing benchmark rates are no longer available, or in certain other circumstances, in which an alternative rate may be required. At June 30, 2024 and December 31, 2023, the Company had no borrowings under this facility. In October 2023, the Company terminated its one-year uncommitted revolving credit facility ("Uncommitted Credit Facility"). At June 30, 2023, the Company had $200 million borrowings outstanding under this facility with a weighted average interest rate of 5.50%. The Company also maintains other credit and overdraft facilities with various financial institutions aggregating $118 million and $113 million, at June 30, 2024 and December 31, 2023, respectively. There were no outstanding borrowings under these facilities at June 30, 2024 and December 31, 2023. The Company also has outstanding guarantees and letters of credit with various banks aggregating $143 million and $139 million, at June 30, 2024 and December 31, 2023, respectively. Senior Notes In June 2024, the Company repaid $600 million of 3.50% senior notes at maturity. In March 2024, the Company repaid $1 billion of 3.875% senior notes at maturity. In February 2024, the Company issued $500 million of 5.150% senior notes due 2034 and $500 million of 5.450% senior notes due 2054. The Company used the net proceeds from these issuances for general corporate purposes. In October 2023, the Company repaid $250 million of 4.05% senior notes at maturity. In September 2023, the Company issued $600 million of 5.400% senior notes due 2033 and $1 billion of 5.700% senior notes due 2053. In March 2023, the Company issued $600 million of 5.450% senior notes due 2053. The Company used the net proceeds from this issuance for general corporate purposes. Fair Value of Short-term and Long-term Debt The estimated fair value of the Company's short-term and long-term debt is provided below. Certain estimates and judgments were required to develop the fair value amounts. The fair value amounts shown below are not necessarily indicative of the amounts that the Company would realize upon disposition, nor do they indicate the Company’s intent or need to dispose of the financial instrument. June 30, 2024 December 31, 2023 (In millions) Carrying Fair Carrying Fair Short-term debt $ 1,267 $ 1,261 $ 1,619 $ 1,610 Long-term debt $ 12,278 $ 11,707 $ 11,844 $ 11,723 The fair value of the Company's short-term debt consists primarily of commercial and term debt maturing within the next year and its fair value approximates its carrying value. The estimated fair value of a primary portion of the Company's long-term debt is based on discounted future cash flows using current interest rates available for debt with similar terms and remaining maturities. Short-term and long-term debt would be classified as Level 2 in the fair value hierarchy.

Restructuring Costs

Restructuring Costs	6 Months Ended
	Jun. 30, 2024
Restructuring and Related Activities [Abstract]
Restructuring Costs	Restructuring Costs In the fourth quarter of 2022, the Company initiated activities focused on workforce actions, rationalization of technology and functional services, and reductions in real estate. For the three and six months ended June 30, 2024, the Company has incurred $30 million and $60 million, respectively, of restructuring costs related to these activities, primarily severance. Any remaining costs are expected to be incurred by the end of 2024. The Company incurred a total of $44 million and $86 million for restructuring activities for the three and six months ended June 30, 2024, respectively, compared to $65 million and $118 million, for the corresponding periods in the prior year. The Company incurred costs related to these initiatives as follows: Three Months Ended Six Months Ended (In millions) 2024 2023 2024 2023 Risk and Insurance Services $ 29 $ 31 $ 51 $ 63 Consulting 5 7 16 16 Corporate 10 27 19 39 Total $ 44 $ 65 $ 86 $ 118 Details of the restructuring activity from January 1, 2023 through June 30, 2024, are as follows: (In millions) Severance Real Estate Related Costs (a) Information Technology Consulting and Other Outside Services Total Liability at January 1, 2023 $ 88 $ 56 $ — $ 2 $ 146 2023 charges 148 96 15 42 301 Cash payments (147) (69) (13) (42) (271) Non-cash charges — (44) (2) — (46) Liability at December 31, 2023 $ 89 $ 39 $ — $ 2 $ 130 2024 charges 42 21 11 12 86 Cash payments (102) (26) (11) (14) (153) Non-cash charges — (3) — — (3) Liability at June 30, 2024 $ 29 $ 31 $ — $ — $ 60 (a) Includes ROU and fixed asset impairments and other real estate related costs.

Common Stock

Common Stock	6 Months Ended
	Jun. 30, 2024
Equity [Abstract]
Common Stock	Common Stock The Company has a share repurchases program authorized by the Board of Directors. For the first six months of 2024, the Company repurchased 3.0 million shares of its common stock for $600 million. At June 30, 2024, the Company remained authorized to repurchase up to approximately $2.6 billion in shares of its common stock. There is no time limit on the authorization. For the first six months of 2023, the Company repurchased 3.5 million shares of its common stock for $600 million. The Company issued approximately 2.9 million and 2.8 million shares related to stock compensation and employee stock purchase plans for the first six months of 2024 and 2023, respectively. In January and March of 2024, the Board of Directors of the Company declared quarterly dividends of $0.710 per share on outstanding common stock, which were paid in February and May 2024, respectively. In July 2024, the Board of Directors of the Company declared a quarterly dividend of $0.815 per share on outstanding common stock, payable in August 2024.

Claims, Lawsuits and Other Cont

Claims, Lawsuits and Other Contingencies	6 Months Ended
	Jun. 30, 2024
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, 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. In June 2023, White Oak, one such 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 November 2023, Credit Suisse, another loss payee, added Marsh Ltd. as a party to the omnibus trade credit insurance policy litigation among Greensill and its insurers and loss payees in Australia. The claims by both loss payees allege that Marsh Ltd., which was not the insurance broker for either White Oak or Credit Suisse, failed to take required steps to make complete and accurate representations to them in their respective capacities as loss payees. 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.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2024
Segment Reporting [Abstract]
Segment Information	Segment Information The Company is organized based on the types of services provided. Under this structure, the Company’s segments are: • Risk and Insurance Services , comprising insurance services (Marsh) and reinsurance services (Guy Carpenter); and • Consulting , comprising Mercer and Oliver Wyman Group. The accounting policies of the segments are the same as those used for the consolidated financial statements described in Note 1, Summary of Significant Accounting Policies, in the Company’s 2023 Form 10-K. Segment performance is evaluated based on segment operating income, which includes directly related expenses, and charges or credits related to restructuring but not the Company’s corporate-level expenses. Revenues are attributed to geographic areas on the basis of where the services are performed. Selected information about the Company’s segments for the three and six months ended June 30, 2024 and 2023 is as follows: Three Months Ended Six Months Ended (In millions) Revenue Operating Income/(Loss) Revenue Operating Income/(Loss) 2024 – Risk and Insurance Services $ 4,022 (a) $ 1,297 $ 8,295 (c) $ 2,862 Consulting 2,216 (b) 410 4,430 (d) 842 Total Segments 6,238 1,707 12,725 3,704 Corporate/Eliminations (17) (65) (31) (137) Total Consolidated $ 6,221 $ 1,642 $ 12,694 $ 3,567 2023 – Risk and Insurance Services $ 3,722 (a) $ 1,157 $ 7,628 (c) $ 2,552 Consulting 2,172 (b) 388 4,203 (d) 799 Total Segments 5,894 1,545 11,831 3,351 Corporate/Eliminations (18) (88) (31) (168) Total Consolidated $ 5,876 $ 1,457 $ 11,800 $ 3,183 (a) Includes inter-segment revenue of $4 million and $5 million in 2024 and 2023, respectively, interest income on fiduciary funds of $125 million and $108 million in 2024 and 2023, respectively, and equity method income of $10 million and $12 million in 2024 and 2023, respectively. (b) Includes inter-segment revenue of $13 million in 2024 and 2023. (c) Includes inter-segment revenue of $5 million in both 2024 and 2023, interest income on fiduciary funds of $247 million and $199 million in 2024 and 2023, respectively, and equity method income of $10 million and $11 million in 2024 and 2023, respectively. (d) Includes inter-segment revenue of $26 million in both 2024 and 2023. Revenue in 2024 also includes a net gain of $21 million from the sale of Mercer's U.K. pension administration and U.S. health and benefits administration businesses. Details of operating segment revenue for the three and six months ended June 30, 2024 and 2023 are as follows: Three Months Ended Six Months Ended (In millions) 2024 2023 2024 2023 Risk and Insurance Services Marsh $ 3,342 $ 3,103 $ 6,423 $ 5,903 Guy Carpenter 680 619 1,872 1,725 Total Risk and Insurance Services 4,022 3,722 8,295 7,628 Consulting Mercer 1,379 1,374 2,804 2,718 Oliver Wyman Group 837 798 1,626 1,485 Total Consulting 2,216 2,172 4,430 4,203 Total Segments 6,238 5,894 12,725 11,831 Corporate Eliminations (17) (18) (31) (31) Total $ 6,221 $ 5,876 $ 12,694 $ 11,800

New Accounting Pronouncements

New Accounting Pronouncements	6 Months Ended
	Jun. 30, 2024
Accounting Standards Update and Change in Accounting Principle [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements Recently Issued Accounting Pronouncements Not Yet Adopted In December 2023, the FASB issued an accounting standard update on income tax disclosures, primarily related to the rate reconciliation and income taxes paid information. The new guidance requires that public business entities, on an annual basis, disclose specific categories in the rate reconciliation and provide additional information for reconciling items that meet a quantitative threshold. In addition, all entities are required to disclose on an annual basis the amount of income taxes paid, net of refunds received, disaggregated by federal, state and foreign taxes, and by individual jurisdictions if the amount is equal to or greater than 5% of total income taxes paid, net of refunds received. The guidance is effective for annual periods beginning after December 15, 2024. Early adoption is permitted. An entity should apply the amendments in the standard prospectively, even though retrospective application is permitted. The Company is currently evaluating the guidance and expects it to only impact disclosures with no impact to results of operations, cash flows, or financial condition.

Principles of Consolidation a_2

Principles of Consolidation and Other Matters (Policies)	6 Months Ended
	Jun. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents
Allowance for Credit Losses on Accounts Receivable	Allowance for Credit Losses on Accounts Receivable
Investments	Investments The caption "Investment income" in the consolidated statements of income comprises realized and unrealized gains and losses from investments recognized in earnings. It includes, when applicable, other than temporary declines in the value of securities, mark-to-market increases or decreases in equity investments with readily determinable fair values and equity method gains or losses on the Company's investments in private equity funds.
Income Taxes	Income Taxes The Company's effective tax rate for the three months ended June 30, 2024 was 27.1%, compared with 24.4% for the corresponding quarter of 2023. The effective tax rates for the six months ended June 30, 2024 and 2023 were 25.4% and 24.6%, respectively. The tax rate in each period reflects the impact of discrete tax items such as excess tax benefits related to share-based compensation, enacted tax legislation, changes in uncertain tax positions, deferred tax adjustments, non-taxable adjustments related to contingent consideration for acquisitions, and valuation allowances for certain tax credits and attributes. The rate for the three and six months ended June 30, 2024 reflects the previously enacted change in the United Kingdom (U.K.) corporate income tax rate from 19% to 25%, which was effective April 1, 2023. The blended U.K. statutory tax rate for 2023 was 23.5%. The excess tax benefit related to share-based payments is the most significant discrete item in both periods, reducing the effective tax rate by 0.7% and 1.2% for the three months ended June 30, 2024 and 2023, respectively, and by 1.6% and 1.3% for the six months periods ended June 30, 2024 and 2023, respectively. The Company's tax rate reflects its income, statutory tax rates, and tax planning in the various jurisdictions in which it operates. Significant judgment is required in determining the annual effective tax rate and in evaluating uncertain tax positions. Losses in one jurisdiction, generally, cannot offset earnings in another, and within certain jurisdictions profits and losses may not offset between entities. Consequently, losses in certain jurisdictions may require valuation allowances affecting the effective tax rate, depending on estimates of the realizability of associated deferred tax assets. The tax rate is also sensitive to changes in unrecognized tax benefits, including the impact of settled tax audits and expired statutes of limitations. The Company reports a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in tax returns. The Company's gross unrecognized tax benefits were $119 million at June 30, 2024, and $124 million at December 31, 2023. It is reasonably possible that the total amount of unrecognized tax benefits could decrease up to approximately $66 million within the next twelve months due to settlement of audits and expirations of statutes of limitations.
Restructuring Costs	Restructuring Costs Charges associated with restructuring activities are recognized in accordance with applicable accounting guidance which includes accounting for disposal or exit activities, guidance related to impairment of right-of-use ("ROU") assets related to real estate leases, as well as other costs resulting from accelerated depreciation or amortization of leasehold improvements and other property and equipment. Severance and related costs are recognized based on amounts due under established severance plans or estimates of one-time benefits that will be provided. Typically, severance benefits are recognized when the impacted colleagues are notified of their expected termination and such termination is expected to occur within the legally required notification period. These costs are included in compensation and benefits in the consolidated statements of income. Costs for real estate consolidation are recognized based on the type of cost, and the expected future use of the facility. For locations where the Company does not expect to sub-lease the property, the amortization of any ROU asset is accelerated from the decision date to the cease use date. For locations where the Company expects to sub-lease the properties subsequent to its vacating the property, the ROU asset is reviewed for potential impairment at the earlier of the cease use date or the date a sub-lease is signed. To determine the amount of impairment, the fair value of the ROU asset is determined based on the present value of the estimated net cash flows related to the property. Contractual costs outside of the ROU asset are recognized based on the net present value of expected future cash outflows for which the Company will not receive any benefit. Such amounts are reliant on estimates of future sub-lease income to be received and future contractual costs to be incurred. These costs are included in other operating expenses in the consolidated statements of income. Other costs related to restructuring, such as moving, legal or consulting costs are recognized as incurred. These costs are included in other operating expenses in the consolidated statements of income.
Foreign Currency	Foreign Currency
Revenue	Revenue The core principle of the revenue recognition guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this principle, the entity applies the following steps: identify the contract(s) with the customer, identify the performance obligations in the contract(s), determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when (or as) the entity satisfies a performance obligation. In accordance with the accounting guidance, a performance obligation is satisfied either at a "point in time" or "over time", depending on the nature of the product or service provided, and the specific terms of the contract with customers.
Fair Value Measurement	Fair Value Hierarchy The Company has categorized its assets and liabilities that are valued at fair value on a recurring basis into a three-level fair value hierarchy. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets and liabilities (Level 1) and lowest priority to unobservable inputs (Level 3). In some cases, the inputs used to measure fair value might fall into different levels of the fair value hierarchy. In such cases, the level in the fair value hierarchy, for disclosure purposes, is determined based on the lowest level input that is significant to the fair value measurement. Assets and liabilities recorded in the consolidated balance sheets at fair value are categorized based on the inputs in the valuation techniques as follows: Level 1. Assets and liabilities whose values are based on unadjusted quoted prices for identical assets or liabilities in an active market (examples include active exchange-traded equity securities and exchange-traded money market mutual funds). Assets and liabilities measured using Level 1 inputs include exchange-traded equity securities, exchange-traded mutual funds and money market funds. Level 2. Assets and liabilities whose values are based on the following: a) quoted prices for similar assets or liabilities in active markets; b) quoted prices for identical or similar assets or liabilities in non-active markets (examples include corporate and municipal bonds, which trade infrequently); c) pricing models whose inputs are observable for substantially the full term of the asset or liability (examples include most over-the-counter derivatives, including interest rate and currency swaps); and d) pricing models whose inputs are derived principally from or corroborated by observable market data through correlation or other means for substantially the full asset or liability (for example, certain mortgage loans). Level 3. Assets and liabilities whose values are based on prices, or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs reflect management’s own assumptions about the assumptions a market participant would use in pricing the asset or liability. Assets and liabilities measured using Level 3 inputs relate to assets and liabilities for contingent purchase consideration. Valuation Techniques Equity Securities, Money Market Funds and Mutual Funds – Level 1 Investments for which market quotations are readily available are valued at the sale price on their principal exchange or, for certain markets, official closing bid price. Money market funds are valued at a readily determinable price. Contingent Purchase Consideration Assets and Liabilities – Level 3 Purchase consideration for some acquisitions and dispositions made by the Company include contingent consideration arrangements. Contingent consideration arrangements are based primarily on EBITDA or revenue targets over a period of 2 to 4 years. The fair value of the contingent purchase consideration asset and liability is estimated as the present value of future cash flows to be paid, based on projections of revenue and earnings and related targets of the acquired and disposed entities.
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Issued Accounting Pronouncements Not Yet Adopted In December 2023, the FASB issued an accounting standard update on income tax disclosures, primarily related to the rate reconciliation and income taxes paid information. The new guidance requires that public business entities, on an annual basis, disclose specific categories in the rate reconciliation and provide additional information for reconciling items that meet a quantitative threshold. In addition, all entities are required to disclose on an annual basis the amount of income taxes paid, net of refunds received, disaggregated by federal, state and foreign taxes, and by individual jurisdictions if the amount is equal to or greater than 5% of total income taxes paid, net of refunds received. The guidance is effective for annual periods beginning after December 15, 2024. Early adoption is permitted. An entity should apply the amendments in the standard prospectively, even though retrospective application is permitted. The Company is currently evaluating the guidance and expects it to only impact disclosures with no impact to results of operations, cash flows, or financial condition.

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Jun. 30, 2024
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	The following table disaggregates various components of the Company's revenue: Three Months Ended Six Months Ended (In millions) 2024 2023 2024 2023 Marsh: EMEA $ 912 $ 858 $ 1,937 $ 1,790 Asia Pacific 391 357 727 669 Latin America 137 137 262 252 Total International 1,440 1,352 2,926 2,711 U.S./Canada 1,825 1,686 3,342 3,071 Total Marsh 3,265 3,038 6,268 5,782 Guy Carpenter 632 576 1,780 1,647 Subtotal 3,897 3,614 8,048 7,429 Fiduciary interest income 125 108 247 199 Total Risk and Insurance Services $ 4,022 $ 3,722 $ 8,295 $ 7,628 Mercer: Wealth $ 612 $ 637 $ 1,284 $ 1,218 Health 547 518 1,085 1,063 Career 220 219 435 437 Total Mercer 1,379 1,374 2,804 2,718 Oliver Wyman Group 837 798 1,626 1,485 Total Consulting $ 2,216 $ 2,172 $ 4,430 $ 4,203
Schedule of Contract Assets and Liabilities	The following table provides contract assets and contract liabilities information from contracts with customers: (In millions) June 30, 2024 December 31, 2023 Contract assets $ 430 $ 357 Contract liabilities $ 885 $ 869

Per Share Data (Tables)

Per Share Data (Tables)	6 Months Ended
	Jun. 30, 2024
Earnings Per Share [Abstract]
Schedule of Basic and Diluted EPS Calculation	Basic and Diluted EPS Calculation Three Months Ended Six Months Ended (In millions, except per share data) 2024 2023 2024 2023 Net income before non-controlling interests $ 1,140 $ 1,047 $ 2,564 $ 2,299 Less: Net income attributable to non-controlling interests 15 12 39 29 Net income attributable to the Company $ 1,125 $ 1,035 $ 2,525 $ 2,270 Basic weighted average common shares outstanding 492 495 492 495 Dilutive effect of potentially issuable common shares 4 4 5 4 Diluted weighted average common shares outstanding 496 499 497 499 Average stock price used to calculate common stock equivalents $ 205.67 $ 177.33 $ 202.53 $ 172.13

Supplemental Disclosures to t_2

Supplemental Disclosures to the Consolidated Statements of Cash Flows (Tables)	6 Months Ended
	Jun. 30, 2024
Supplemental Cash Flow Information [Abstract]
Schedule of Additional Information Concerning Acquisitions, Interest and Income Taxes Paid	The following table provides additional information concerning acquisitions, interest and income taxes paid for the six months ended June 30, 2024 and 2023: (In millions) 2024 2023 Assets acquired, excluding cash, cash equivalents, and cash and cash equivalents held in a fiduciary capacity $ 721 $ 364 Fiduciary liabilities assumed (5) (1) Liabilities assumed (18) (63) Contingent/deferred purchase consideration (54) (8) Net cash outflow for acquisitions $ 644 $ 292 (In millions) 2024 2023 Interest paid $ 295 $ 245 Income taxes paid, net of refunds $ 658 $ 504 The following amounts are included in the consolidated statements of cash flows as operating and financing activities: For the Six Months Ended June 30, (In millions) 2024 2023 Operating: Contingent consideration payments for prior year acquisitions $ (90) $ (41) Receipt of contingent consideration for dispositions — 1 Acquisition/disposition related net charges for adjustments 15 17 Adjustments and payments related to contingent consideration $ (75) $ (23) Financing: Contingent consideration for prior year acquisitions $ (71) $ (134) Deferred consideration related to prior year acquisitions (10) (51) Payments of deferred and contingent consideration for acquisitions $ (81) $ (185) Receipts of contingent consideration for dispositions $ 1 $ 2

Other Comprehensive (Loss) In_2

Other Comprehensive (Loss) Income (Tables)	6 Months Ended
	Jun. 30, 2024
Equity [Abstract]
Schedule of Accumulated Other Comprehensive (Loss) Income	The changes, net of tax, in the balances of each component of AOCI for the three and six months ended June 30, 2024 and 2023, including amounts reclassified out of AOCI, are as follows: (In millions) Pension/Post-Retirement Plans Gains (Losses) Foreign Currency Translation Adjustments Total Balance at April 1, 2024 $ (3,064) $ (2,445) $ (5,509) Other comprehensive income (loss) before reclassifications 9 (32) (23) Amounts reclassified from accumulated other comprehensive income 5 — 5 Net current period other comprehensive income (loss) 14 (32) (18) Balance at June 30, 2024 (a) $ (3,050) $ (2,477) $ (5,527) (In millions) Pension/Post-Retirement Plans Gains (Losses) Foreign Currency Translation Adjustments Total Balance at April 1, 2023 $ (2,766) $ (2,468) $ (5,234) Other comprehensive (loss) income before reclassifications (48) 224 176 Amounts reclassified from accumulated other comprehensive income 3 — 3 Net current period other comprehensive (loss) income (45) 224 179 Balance at June 30, 2023 (a) $ (2,811) $ (2,244) $ (5,055) (a) At June 30, 2024 and 2023, balances are net of deferred tax assets in pension and post-retirement plans gains (losses) of $1.5 billion and $1.4 billion, respectively. (In millions) Pension/Post-Retirement Plans Gains (Losses) Foreign Currency Translation Adjustments Total Balance at January 1, 2024 $ (3,101) $ (2,194) $ (5,295) Other comprehensive income (loss) before reclassifications 42 (283) (241) Amounts reclassified from accumulated other comprehensive income 9 — 9 Net current period other comprehensive income (loss) 51 (283) (232) Balance at June 30, 2024 (a) $ (3,050) $ (2,477) $ (5,527) (In millions) Pension/Post-Retirement Plans Gains (Losses) Foreign Currency Translation Adjustments Total Balance at January 1, 2023 $ (2,721) $ (2,593) $ (5,314) Other comprehensive (loss) income before reclassifications (96) 349 253 Amounts reclassified from accumulated other comprehensive income 6 — 6 Net current period other comprehensive (loss) income (90) 349 259 Balance at June 30, 2023 (a) $ (2,811) $ (2,244) $ (5,055) (a) At June 30, 2024 and 2023, balances are net of deferred tax assets in pension and post-retirement plans gains (losses) of $1.5 billion and $1.4 billion, respectively.
Schedule of Components of Comprehensive (Loss) Income	The components of other comprehensive (loss) income for the three and six months ended June 30, 2024 and 2023 are as follows: Three Months Ended June 30, 2024 2023 (In millions) Pre-Tax Tax Net of Tax Pre-Tax Tax (Credit) Net of Tax Foreign currency translation adjustments $ (28) $ 4 $ (32) $ 223 $ (1) $ 224 Pension/post-retirement plans: Amortization of (gains) losses included in net benefit (credit) cost: Prior service credits (a) (1) — (1) (1) — (1) Net actuarial losses (a) 7 1 6 5 1 4 Subtotal 6 1 5 4 1 3 Foreign currency translation adjustments 12 3 9 (59) (16) (43) Other adjustments — — — (7) (2) (5) Pension/post-retirement plans gains (losses) 18 4 14 (62) (17) (45) Other comprehensive (loss) income $ (10) $ 8 $ (18) $ 161 $ (18) $ 179 (a) Included in other net benefit credits in the consolidated statements of income. Income tax expense on net actuarial losses are included in income tax expense. Six Months Ended June 30, 2024 2023 (In millions) Pre-Tax Tax Net of Tax Pre-Tax Tax (Credit) Net of Tax Foreign currency translation adjustments $ (272) $ 11 $ (283) $ 342 $ (7) $ 349 Pension/post-retirement plans: Amortization of (gains) losses included in net benefit (credit) cost: Prior service credits (a) (1) — (1) (1) — (1) Net actuarial losses (a) 13 3 10 10 3 7 Subtotal 12 3 9 9 3 6 Foreign currency translation adjustments 56 14 42 (122) (31) (91) Other adjustments — — — (7) (2) (5) Pension/post-retirement plans gains (losses) 68 17 51 (120) (30) (90) Other comprehensive (loss) income $ (204) $ 28 $ (232) $ 222 $ (37) $ 259 (a) Included in other net benefit credits in the consolidated statements of income. Income tax expense on net actuarial losses are included in income tax expense.

Acquisitions and Dispositions (

Acquisitions and Dispositions (Tables)	6 Months Ended
	Jun. 30, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Schedule for Allocation of Acquisition Costs	The following table presents the preliminary allocation of purchase consideration to the assets acquired and liabilities assumed in 2024, based on the estimated fair values for the acquisitions as of their respective acquisition dates. Amounts in the table primarily reflect the impact of the Fisher Brown Bottrell Insurance, Inc. and Vanguard acquisitions. Acquisitions through June 30, 2024 (In millions) Cash $ 662 Estimated fair value of deferred/contingent purchase consideration 54 Total consideration $ 716 Allocation of purchase price: Cash and cash equivalents $ 13 Cash and cash equivalents held in a fiduciary capacity 5 Net receivables 49 Other current assets 22 Goodwill 430 Other intangible assets 215 Fixed assets, net 3 Other assets 2 Total assets acquired 739 Current liabilities 9 Fiduciary liabilities 5 Other liabilities 9 Total liabilities assumed 23 Net assets acquired $ 716
Schedule of Acquired Finite-Lived Intangible Assets by Major Class	The following table provides information about other intangible assets acquired in 2024: Other intangible assets through June 30, 2024 (In millions) Amount Weighted Average Amortization Period Client relationships $ 205 11.8 years Other 10 2.8 years Total other intangible assets $ 215
Schedule of Pro-Forma Information	The following unaudited pro-forma financial data gives effect to the acquisitions made by the Company in 2024 and 2023. In accordance with accounting guidance related to pro-forma disclosures, the information presented for acquisitions made in 2024 is as if they occurred on January 1, 2023, and reflects acquisitions made in 2023, as if they occurred on January 1, 2022. The unaudited pro-forma information includes the effects of amortization of acquired intangibles in all years. The unaudited pro-forma financial data is presented for illustrative purposes only and is not necessarily indicative of the operating results that would have been achieved if such acquisitions had occurred on the dates indicated, nor is it necessarily indicative of future consolidated results. Three Months Ended Six Months Ended (In millions, except per share data) 2024 2023 2024 2023 Revenue $ 6,234 $ 5,989 $ 12,756 $ 12,060 Net income attributable to the Company $ 1,135 $ 1,065 $ 2,546 $ 2,317 Basic net income per share attributable to the Company $ 2.31 $ 2.15 $ 5.17 $ 4.68 Diluted net income per share attributable to the Company $ 2.29 $ 2.13 $ 5.13 $ 4.64

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	6 Months Ended
	Jun. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in the Carrying Amount of Goodwill	Changes in the carrying amount of goodwill are as follows: (In millions) 2024 2023 Balance at January 1, $ 17,231 $ 16,251 Goodwill acquired 430 236 Other adjustments (a) (145) 134 Balance at June 30, $ 17,516 $ 16,621 (a) Primarily reflects the impact of foreign exchange.
Schedule of Amortized Intangible Assets	The gross cost and accumulated amortization of other identified intangible assets at June 30, 2024 and December 31, 2023 are as follows: June 30, 2024 December 31, 2023 (In millions) Gross Accumulated Net Gross Accumulated Net Client relationships $ 4,498 $ 1,905 $ 2,593 $ 4,337 $ 1,761 $ 2,576 Other (a) 376 331 45 391 337 54 Other intangible assets $ 4,874 $ 2,236 $ 2,638 $ 4,728 $ 2,098 $ 2,630 (a) Primarily reflects non-compete agreements, trade names and developed technology.
Schedule of Estimated Future Aggregate Amortization Expense	The estimated future aggregate amortization expense is as follows: For the Years Ending December 31, (In millions) Estimated Expense 2024 (excludes amortization through June 30, 2024) $ 174 2025 322 2026 301 2027 293 2028 271 Subsequent years 1,277 Total future amortization $ 2,638

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2024
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following fair value hierarchy table presents information about the Company’s assets and liabilities measured at fair value on a recurring basis at June 30, 2024 and December 31, 2023: Identical Assets Observable Inputs Unobservable Inputs Total (In millions) 06/30/24 12/31/23 06/30/24 12/31/23 06/30/24 12/31/23 06/30/24 12/31/23 Assets: Financial instruments owned: Exchange traded equity securities (a) $ 8 $ 5 $ — $ — $ — $ — $ 8 $ 5 Mutual funds (a) 182 178 — — — — 182 178 Money market funds (b) 354 606 — — — — 354 606 Contingent purchase consideration assets (c) — — — — — 1 — 1 Total assets measured at fair value $ 544 $ 789 $ — $ — $ — $ 1 $ 544 $ 790 Fiduciary Assets: Money market funds $ 65 $ 180 $ — $ — $ — $ — $ 65 $ 180 Total fiduciary assets measured $ 65 $ 180 $ — $ — $ — $ — $ 65 $ 180 Liabilities: Contingent purchase consideration liabilities (d) $ — $ — $ — $ — $ 121 $ 252 $ 121 $ 252 Total liabilities measured at fair value $ — $ — $ — $ — $ 121 $ 252 $ 121 $ 252 (a) Included in other assets in the consolidated balance sheets. (b) Included in cash and cash equivalents in the consolidated balance sheets. (c) Included in other receivables in the consolidated balance sheets. (d) Included in accounts payable and accrued liabilities and other liabilities in the consolidated balance sheets.
Schedule of Changes in Fair Value of Level 3 Liabilities Representing Acquisition Related Contingent Consideration	The following table sets forth a summary of the changes in fair value of the Company’s Level 3 liabilities for the three and six months ended June 30, 2024 and 2023: Three Months Ended Six Months Ended (In millions) 2024 2023 2024 2023 Balance at beginning of period $ 242 $ 383 $ 252 $ 377 Net additions 4 4 17 4 Payments (135) (174) (161) (175) Revaluation impact 9 10 15 17 Other 1 — (2) — Balance at end of period $ 121 $ 223 $ 121 $ 223

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2024
Leases [Abstract]
Schedule of Lease Cost and Additional Information	The following table provides additional information about the Company’s property leases: Three Months Ended Six Months Ended (In millions) 2024 2023 2024 2023 Lease Cost: Operating lease cost (a) $ 81 $ 81 $ 163 $ 161 Short-term lease cost 2 2 3 3 Variable lease cost 28 26 54 63 Sublease income (5) (2) (8) (6) Net lease cost $ 106 $ 107 $ 212 $ 221 Other information: Operating cash outflows from operating leases $ 183 $ 189 Right of use assets obtained in exchange for new operating lease liabilities $ 85 $ 121 Weighted average remaining lease term – real estate 7.8 years 8.3 years Weighted average discount rate – real estate leases 3.58 % 3.21 % (a) Excludes ROU asset impairment charges.
Schedule of Future Minimum Lease Payments for Operating Leases	Future minimum lease payments for the Company’s operating leases at June 30, 2024 are as follows: (In millions) Real Estate Leases 2024 (excludes payments through June 30, 2024) $ 182 2025 355 2026 327 2027 289 2028 214 2029 170 Subsequent years 616 Total future lease payments 2,153 Less: Imputed interest (263) Total $ 1,890 Current lease liabilities $ 304 Long-term lease liabilities 1,586 Total lease liabilities $ 1,890 Note: The above table excludes obligations for leases with original terms of 12 months or less which have not been recognized as a ROU asset or liability in the consolidated balance sheets.

Retirement Benefits (Tables)

Retirement Benefits (Tables)	6 Months Ended
	Jun. 30, 2024
Retirement Benefits [Abstract]
Schedule of Weighted Average Actuarial Assumptions Utilized to Calculate the Net Periodic Benefit Costs	The weighted average actuarial assumptions utilized to calculate the net periodic benefit costs for the U.S. and significant non-U.S. defined benefit plans are as follows: Combined U.S. and significant non-U.S. Plans Pension Benefits June 30, 2024 2023 Weighted average assumptions: Expected return on plan assets 5.44 % 5.31 % Discount rate 4.95 % 5.16 % Rate of compensation increase * 3.16 % 3.16 % (*) There are no rate of compensation increase assumptions for the U.S. defined benefit plans since future benefit accruals were discontinued for those plans after December 31, 2016 and earned benefits are not subject to final salary level adjustments.
Schedule of Net Benefit Costs	The components of the net benefit credit for defined benefit plans are as follows: Combined U.S. and significant non-U.S. Plans For the Three Months Ended June 30, Pension Benefits (In millions) 2024 2023 Service cost $ 6 $ 5 Interest cost 144 150 Expected return on plan assets (216) (215) Amortization of prior service (credit) cost 1 — Recognized actuarial loss 7 5 Net benefit credit $ (58) $ (55) Combined U.S. and significant non-U.S. Plans For the Six Months Ended June 30, Pension Benefits (In millions) 2024 2023 Service cost $ 12 $ 11 Interest cost 288 298 Expected return on plan assets (435) (427) Amortization of prior service (credit) cost 1 — Recognized actuarial loss 15 11 Net benefit credit $ (119) $ (107) The following tables provide the amounts reported in the consolidated statements of income: Combined U.S. and significant non-U.S. Plans For the Three Months Ended June 30, Pension Benefits (In millions) 2024 2023 Compensation and benefits expense $ 6 $ 5 Other net benefit credits (64) (60) Net benefit credit $ (58) $ (55) Combined U.S. and significant non-U.S. Plans For the Six Months Ended June 30, Pension Benefits (In millions) 2024 2023 Compensation and benefits expense $ 12 $ 11 Other net benefit credits (131) (118) Net benefit credit $ (119) $ (107) The components of the net benefit credit for the U.S. defined benefit plans are as follows: U.S. Plans only For the Three Months Ended June 30, Pension Benefits (In millions) 2024 2023 Interest cost $ 63 $ 65 Expected return on plan assets (75) (77) Recognized actuarial loss 5 4 Net benefit credit $ (7) $ (8) U.S. Plans only For the Six Months Ended June 30, Pension Benefits (In millions) 2024 2023 Interest cost $ 125 $ 130 Expected return on plan assets (151) (155) Recognized actuarial loss 10 9 Net benefit credit $ (16) $ (16) The components of the net benefit credit for the non-U.S. defined benefit plans are as follows: Significant non-U.S. Plans only For the Three Months Ended June 30, Pension Benefits (In millions) 2024 2023 Service cost $ 6 $ 5 Interest cost 81 85 Expected return on plan assets (141) (138) Amortization of prior service credit 1 — Recognized actuarial loss 2 1 Net benefit credit $ (51) $ (47) Significant non-U.S. Plans only For the Six Months Ended June 30, Pension Benefits (In millions) 2024 2023 Service cost $ 12 $ 11 Interest cost 163 168 Expected return on plan assets (284) (272) Amortization of prior service credit 1 — Recognized actuarial loss 5 2 Net benefit credit $ (103) $ (91)

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2024
Debt Disclosure [Abstract]
Schedule of Outstanding Debt	The Company’s outstanding debt is as follows: (In millions) June 30, December 31, 2023 Short-term: Commercial paper $ 749 $ — Current portion of long-term debt 518 1,619 $ 1,267 $ 1,619 Long-term: Senior notes – 3.50% due 2024 $ — $ 600 Senior notes – 3.875% due 2024 — 1,000 Senior notes – 3.50% due 2025 500 499 Senior notes – 1.349% due 2026 593 617 Senior notes – 3.75% due 2026 599 599 Senior notes – 4.375% due 2029 1,499 1,499 Senior notes – 1.979% due 2030 578 601 Senior notes – 2.25% due 2030 742 741 Senior notes – 2.375% due 2031 397 397 Senior notes – 5.750% due 2032 493 493 Senior notes – 5.875% due 2033 298 298 Senior notes – 5.400% due 2033 592 592 Senior notes – 5.150% due 2034 495 — Senior notes – 4.75% due 2039 496 496 Senior notes – 4.35% due 2047 494 494 Senior notes – 4.20% due 2048 593 593 Senior notes – 4.90% due 2049 1,239 1,239 Senior notes – 2.90% due 2051 346 346 Senior notes – 6.25% due 2052 491 491 Senior notes – 5.450% due 2053 591 591 Senior notes – 5.700% due 2053 988 988 Senior notes – 5.450% due 2054 493 — Mortgage – 5.70% due 2035 276 284 Other 3 5 12,796 13,463 Less: current portion 518 1,619 $ 12,278 $ 11,844
Schedule of Estimated Fair Value of Significant Financial Instruments	The fair value amounts shown below are not necessarily indicative of the amounts that the Company would realize upon disposition, nor do they indicate the Company’s intent or need to dispose of the financial instrument. June 30, 2024 December 31, 2023 (In millions) Carrying Fair Carrying Fair Short-term debt $ 1,267 $ 1,261 $ 1,619 $ 1,610 Long-term debt $ 12,278 $ 11,707 $ 11,844 $ 11,723

Restructuring Costs (Tables)

Restructuring Costs (Tables)	6 Months Ended
	Jun. 30, 2024
Restructuring and Related Activities [Abstract]
Schedule of Restructuring and Related Costs Incurred	The Company incurred costs related to these initiatives as follows: Three Months Ended Six Months Ended (In millions) 2024 2023 2024 2023 Risk and Insurance Services $ 29 $ 31 $ 51 $ 63 Consulting 5 7 16 16 Corporate 10 27 19 39 Total $ 44 $ 65 $ 86 $ 118
Schedule of Restructuring Activities	Details of the restructuring activity from January 1, 2023 through June 30, 2024, are as follows: (In millions) Severance Real Estate Related Costs (a) Information Technology Consulting and Other Outside Services Total Liability at January 1, 2023 $ 88 $ 56 $ — $ 2 $ 146 2023 charges 148 96 15 42 301 Cash payments (147) (69) (13) (42) (271) Non-cash charges — (44) (2) — (46) Liability at December 31, 2023 $ 89 $ 39 $ — $ 2 $ 130 2024 charges 42 21 11 12 86 Cash payments (102) (26) (11) (14) (153) Non-cash charges — (3) — — (3) Liability at June 30, 2024 $ 29 $ 31 $ — $ — $ 60 (a) Includes ROU and fixed asset impairments and other real estate related costs.

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2024
Segment Reporting [Abstract]
Schedule of Selected Information and Details for MMC's Operating Segments	Selected information about the Company’s segments for the three and six months ended June 30, 2024 and 2023 is as follows: Three Months Ended Six Months Ended (In millions) Revenue Operating Income/(Loss) Revenue Operating Income/(Loss) 2024 – Risk and Insurance Services $ 4,022 (a) $ 1,297 $ 8,295 (c) $ 2,862 Consulting 2,216 (b) 410 4,430 (d) 842 Total Segments 6,238 1,707 12,725 3,704 Corporate/Eliminations (17) (65) (31) (137) Total Consolidated $ 6,221 $ 1,642 $ 12,694 $ 3,567 2023 – Risk and Insurance Services $ 3,722 (a) $ 1,157 $ 7,628 (c) $ 2,552 Consulting 2,172 (b) 388 4,203 (d) 799 Total Segments 5,894 1,545 11,831 3,351 Corporate/Eliminations (18) (88) (31) (168) Total Consolidated $ 5,876 $ 1,457 $ 11,800 $ 3,183 (a) Includes inter-segment revenue of $4 million and $5 million in 2024 and 2023, respectively, interest income on fiduciary funds of $125 million and $108 million in 2024 and 2023, respectively, and equity method income of $10 million and $12 million in 2024 and 2023, respectively. (b) Includes inter-segment revenue of $13 million in 2024 and 2023. (c) Includes inter-segment revenue of $5 million in both 2024 and 2023, interest income on fiduciary funds of $247 million and $199 million in 2024 and 2023, respectively, and equity method income of $10 million and $11 million in 2024 and 2023, respectively. (d) Includes inter-segment revenue of $26 million in both 2024 and 2023. Revenue in 2024 also includes a net gain of $21 million from the sale of Mercer's U.K. pension administration and U.S. health and benefits administration businesses.
Schedule of Details of Operating Segment Revenue	Details of operating segment revenue for the three and six months ended June 30, 2024 and 2023 are as follows: Three Months Ended Six Months Ended (In millions) 2024 2023 2024 2023 Risk and Insurance Services Marsh $ 3,342 $ 3,103 $ 6,423 $ 5,903 Guy Carpenter 680 619 1,872 1,725 Total Risk and Insurance Services 4,022 3,722 8,295 7,628 Consulting Mercer 1,379 1,374 2,804 2,718 Oliver Wyman Group 837 798 1,626 1,485 Total Consulting 2,216 2,172 4,430 4,203 Total Segments 6,238 5,894 12,725 11,831 Corporate Eliminations (17) (18) (31) (31) Total $ 6,221 $ 5,876 $ 12,694 $ 11,800

Nature of Operations (Details)

Nature of Operations (Details)	6 Months Ended
	Jun. 30, 2024 segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of business segments (segment)	2

Principles of Consolidation a_3

Principles of Consolidation and Other Matters (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Operating funds related to regulatory requirements or as collateral under captive insurance arrangements	$ 505		$ 505		$ 486
Equity method investments lag period			3 months
Net investment income	$ 1	$ 3	$ 2	$ 5
Effective tax rate (as a percent)	27.10%	24.40%	25.40%	24.60%
Share-based payments of excess tax benefit (as percent)	0.70%	1.20%	1.60%	1.30%
Unrecognized tax benefits	$ 119		$ 119		$ 124
Reasonably possible decrease in unrecognized tax benefits	$ 66		$ 66

Revenue (Narrative) (Details)

Revenue (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenue from Contract with Customer [Abstract]
Threshold percentage of total revenue			1%
Revenue recognized that was included in the contract liability balance at the beginning of the period	$ 266	$ 218	$ 581	$ 511
Performance obligation satisfied in previous period	$ 29	$ 27	$ 43	$ 44

Revenue (Disaggregation of Reve

Revenue (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Revenue	$ 6,221	$ 5,876	$ 12,694	$ 11,800
Total Segments
Disaggregation of Revenue [Line Items]
Revenue	6,238	5,894	12,725	11,831
Risk and Insurance Services | Total Segments
Disaggregation of Revenue [Line Items]
Fiduciary interest income	125	108	247	199
Revenue	4,022	3,722	8,295	7,628
Risk and Insurance Services | Subtotal | Total Segments
Disaggregation of Revenue [Line Items]
Revenue, excluding fiduciary interest income	3,897	3,614	8,048	7,429
Risk and Insurance Services | Total Marsh | Total Segments
Disaggregation of Revenue [Line Items]
Revenue, excluding fiduciary interest income	3,265	3,038	6,268	5,782
Risk and Insurance Services | Guy Carpenter | Total Segments
Disaggregation of Revenue [Line Items]
Revenue, excluding fiduciary interest income	632	576	1,780	1,647
Risk and Insurance Services | Total International | Total Segments
Disaggregation of Revenue [Line Items]
Revenue, excluding fiduciary interest income	1,440	1,352	2,926	2,711
Risk and Insurance Services | EMEA | Total Segments
Disaggregation of Revenue [Line Items]
Revenue, excluding fiduciary interest income	912	858	1,937	1,790
Risk and Insurance Services | Asia Pacific | Total Segments
Disaggregation of Revenue [Line Items]
Revenue, excluding fiduciary interest income	391	357	727	669
Risk and Insurance Services | Latin America | Total Segments
Disaggregation of Revenue [Line Items]
Revenue, excluding fiduciary interest income	137	137	262	252
Risk and Insurance Services | U.S./Canada | Total Segments
Disaggregation of Revenue [Line Items]
Revenue, excluding fiduciary interest income	1,825	1,686	3,342	3,071
Consulting | Total Segments
Disaggregation of Revenue [Line Items]
Revenue	2,216	2,172	4,430	4,203
Consulting | Mercer | Total Segments
Disaggregation of Revenue [Line Items]
Revenue	1,379	1,374	2,804	2,718
Consulting | Mercer | Wealth | Total Segments
Disaggregation of Revenue [Line Items]
Revenue	612	637	1,284	1,218
Consulting | Mercer | Health | Total Segments
Disaggregation of Revenue [Line Items]
Revenue	547	518	1,085	1,063
Consulting | Mercer | Career | Total Segments
Disaggregation of Revenue [Line Items]
Revenue	220	219	435	437
Consulting | Oliver Wyman Group | Total Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 837	$ 798	$ 1,626	$ 1,485

Revenue (Contract Assets and Li

Revenue (Contract Assets and Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Contract assets	$ 430	$ 357
Contract liabilities	$ 885	$ 869

Fiduciary Assets and Liabilit_2

Fiduciary Assets and Liabilities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Fiduciary Assets and Liabilities [Line Items]
Net uncollected premiums and claims receivable and payable	$ 16,900		$ 16,900		$ 13,800
Total Segments | Risk and Insurance Services
Fiduciary Assets and Liabilities [Line Items]
Interest on fiduciary funds	$ 125	$ 108	$ 247	$ 199

Per Share Data (Details)

Per Share Data (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Earnings Per Share [Abstract]
Net income before non-controlling interests	$ 1,140	$ 1,047	$ 2,564	$ 2,299
Less: Net income attributable to non-controlling interests	15	12	39	29
Net income attributable to the Company	$ 1,125	$ 1,035	$ 2,525	$ 2,270
Basic weighted average common shares outstanding (in shares)	492	495	492	495
Dilutive effect of potentially issuable common shares (in shares)	4	4	5	4
Diluted weighted average common shares outstanding (in shares)	496	499	497	499
Average stock price used to calculate common stock equivalents (in dollars per share)	$ 205.67	$ 177.33	$ 202.53	$ 172.13

Supplemental Disclosures to t_3

Supplemental Disclosures to the Consolidated Statements of Cash Flows (Additional Information Concerning Acquisitions, Interest and Income Taxes Paid) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Supplemental Cash Flow Information [Abstract]
Assets acquired, excluding cash, cash equivalents, and cash and cash equivalents held in a fiduciary capacity	$ 721	$ 364
Fiduciary liabilities assumed	(5)	(1)
Liabilities assumed	(18)	(63)
Contingent/deferred purchase consideration	(54)	(8)
Net cash outflow for acquisitions	644	292
Interest paid	295	245
Income taxes paid, net of refunds	$ 658	$ 504

Supplemental Disclosures (Suppl

Supplemental Disclosures (Supplemental Operating and Financing Cash Flow Items) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Operating:
Contingent consideration payments for prior year acquisitions	$ (90)	$ (41)
Receipt of contingent consideration for dispositions	0	1
Acquisition/disposition related net charges for adjustments	15	17
Adjustments and payments related to contingent consideration	(75)	(23)
Financing:
Contingent consideration for prior year acquisitions	(71)	(134)
Deferred consideration related to prior year acquisitions	(10)	(51)
Payments of deferred and contingent consideration for acquisitions	(81)	(185)
Receipts of contingent consideration for dispositions	$ 1	$ 2

Supplemental Disclosures to t_4

Supplemental Disclosures to the Consolidated Statements of Cash Flows (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Supplemental Cash Flow Information [Abstract]
Non-cash issuance of common stock			$ 321	$ 296
Stock-based compensation expense, equity awards	$ 90	$ 92	$ 193	$ 191

Other Comprehensive (Loss) In_3

Other Comprehensive (Loss) Income (Schedule of Accumulated Other Comprehensive (Loss) Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period			$ 12,370
Other comprehensive (loss) income, net of tax	$ (18)	$ 179	(232)	$ 259
Balance, end of period	13,565	12,139	13,565	12,139
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(5,509)	(5,234)	(5,295)	(5,314)
Other comprehensive income (loss) before reclassifications	(23)	176	(241)	253
Amounts reclassified from accumulated other comprehensive income	5	3	9	6
Other comprehensive (loss) income, net of tax	(18)	179	(232)	259
Balance, end of period	(5,527)	(5,055)	(5,527)	(5,055)
Pension/Post-Retirement Plans Gains (Losses)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(3,064)	(2,766)	(3,101)	(2,721)
Other comprehensive income (loss) before reclassifications	9	(48)	42	(96)
Amounts reclassified from accumulated other comprehensive income	5	3	9	6
Other comprehensive (loss) income, net of tax	14	(45)	51	(90)
Balance, end of period	(3,050)	(2,811)	(3,050)	(2,811)
Deferred tax assets, net	1,500	1,400	1,500	1,400
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(2,445)	(2,468)	(2,194)	(2,593)
Other comprehensive income (loss) before reclassifications	(32)	224	(283)	349
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other comprehensive (loss) income, net of tax	(32)	224	(283)	349
Balance, end of period	$ (2,477)	$ (2,244)	$ (2,477)	$ (2,244)

Other Comprehensive (Loss) In_4

Other Comprehensive (Loss) Income (Schedule of Components of Comprehensive (Loss) Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pre-Tax
Other comprehensive (loss) income	$ (10)	$ 161	$ (204)	$ 222
Tax
Other comprehensive (loss) income	8	(18)	28	(37)
Net of Tax
Other comprehensive (loss) income, net of tax	(18)	179	(232)	259
Foreign currency translation adjustments
Pre-Tax
Other comprehensive income (loss), before reclassification	(28)	223	(272)	342
Tax
Other comprehensive income (loss), before reclassification	4	(1)	11	(7)
Net of Tax
Other comprehensive income (loss), before reclassification	(32)	224	(283)	349
Reclassification from AOCI	0	0	0	0
Other comprehensive (loss) income, net of tax	(32)	224	(283)	349
Prior service credits
Pre-Tax
Reclassification from AOCI	(1)	(1)	(1)	(1)
Tax
Reclassification from AOCI	0	0	0	0
Net of Tax
Reclassification from AOCI	(1)	(1)	(1)	(1)
Net actuarial losses
Pre-Tax
Reclassification from AOCI	7	5	13	10
Tax
Reclassification from AOCI	1	1	3	3
Net of Tax
Reclassification from AOCI	6	4	10	7
Pension/post-retirement plans gains (losses)
Pre-Tax
Reclassification from AOCI	6	4	12	9
Other comprehensive (loss) income	18	(62)	68	(120)
Tax
Reclassification from AOCI	1	1	3	3
Other comprehensive (loss) income	4	(17)	17	(30)
Net of Tax
Other comprehensive income (loss), before reclassification	9	(48)	42	(96)
Reclassification from AOCI	5	3	9	6
Other comprehensive (loss) income, net of tax	14	(45)	51	(90)
Foreign currency translation adjustments
Pre-Tax
Other comprehensive income (loss), before reclassification	12	(59)	56	(122)
Tax
Other comprehensive income (loss), before reclassification	3	(16)	14	(31)
Net of Tax
Other comprehensive income (loss), before reclassification	9	(43)	42	(91)
Other adjustments
Pre-Tax
Other comprehensive income (loss), before reclassification	0	(7)	0	(7)
Tax
Other comprehensive income (loss), before reclassification	0	(2)	0	(2)
Net of Tax
Other comprehensive income (loss), before reclassification	$ 0	$ (5)	$ 0	$ (5)

Acquisitions and Dispositions_2

Acquisitions and Dispositions (Narrative) (Details) $ in Millions		3 Months Ended				6 Months Ended		12 Months Ended
	Jan. 01, 2024 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($) acquisition	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Jun. 30, 2024 USD ($) acquisition	Jun. 30, 2023 USD ($)	Dec. 31, 2023 acquisition
Business Acquisition [Line Items]
Total consideration						$ 716	$ 340
Cash paid						662	332
Estimated fair value of deferred/contingent purchase consideration						54	8
Deferred purchase consideration from prior years' acquisitions						10	51
Contingent consideration from prior year's acquisitions						71	134
Cash divested from deconsolidation					$ 20
Purchase of non-controlling interests				$ 139		0	139
Total Segments | Small Individual Financial Advisory Business
Business Acquisition [Line Items]
Net gain (loss) on disposition of business							(17)
Discontinued Operations, Disposed of by Sale | U.S. Health And Benefits And U.K Pension Administration Businesses
Business Acquisition [Line Items]
Cash proceeds from sale	$ 114
Net gain (loss) on disposition of business	$ 21
Exit costs			$ 18
Discontinued Operations, Disposed of by Sale | U.S. Health And Benefits And U.K Pension Administration Businesses | Total Segments
Business Acquisition [Line Items]
Net gain (loss) on disposition of business						21
Prior Fiscal Periods Acquisitions
Business Acquisition [Line Items]
Deferred purchase consideration from prior years' acquisitions							51
Contingent consideration from prior year's acquisitions						161	175
Pro forma revenue				41			41
Operating income (loss) related to acquisitions				9			9
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Total consideration						716
Cash paid						662
Estimated fair value of deferred/contingent purchase consideration						54
Pro forma revenue		$ 48				62
Operating income (loss) related to acquisitions		3				(3)
Westpac Transaction
Business Acquisition [Line Items]
Acquisition related costs		$ 21		$ 10		$ 29	$ 27
Minimum
Business Acquisition [Line Items]
Revenue target period (in years)						2 years	2 years
Maximum
Business Acquisition [Line Items]
Revenue target period (in years)						4 years	4 years
Risk and Insurance Services
Business Acquisition [Line Items]
Number of acquisitions made (in acquisitions) | acquisition						5		9
Consulting
Business Acquisition [Line Items]
Number of acquisitions made (in acquisitions) | acquisition			5			4

Acquisitions and Dispositions_3

Acquisitions and Dispositions (Allocation of Acquisition Costs) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Cash	$ 662	$ 332
Estimated fair value of deferred/contingent purchase consideration	54	8
Total consideration	716	340
Allocation of purchase price:
Goodwill	17,516	$ 16,621	$ 17,231	$ 16,251
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Cash	662
Estimated fair value of deferred/contingent purchase consideration	54
Total consideration	716
Allocation of purchase price:
Cash and cash equivalents	13
Cash and cash equivalents held in a fiduciary capacity	5
Net receivables	49
Other current assets	22
Goodwill	430
Other intangible assets	215
Fixed assets, net	3
Other assets	2
Total assets acquired	739
Current liabilities	9
Fiduciary liabilities	5
Other liabilities	9
Total liabilities assumed	23
Net assets acquired	$ 716

Acquisitions and Dispositions_4

Acquisitions and Dispositions (Acquired Finite-Lived Intangible Assets) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2024 USD ($)
Finite-Lived Intangible Assets [Line Items]
Amount	$ 215
Client relationships
Finite-Lived Intangible Assets [Line Items]
Amount	$ 205
Weighted Average Amortization Period	11 years 9 months 18 days
Other
Finite-Lived Intangible Assets [Line Items]
Amount	$ 10
Weighted Average Amortization Period	2 years 9 months 18 days

Acquisitions and Dispositions_5

Acquisitions and Dispositions (Pro-Forma Information) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Revenue	$ 6,234	$ 5,989	$ 12,756	$ 12,060
Net income attributable to the Company	$ 1,135	$ 1,065	$ 2,546	$ 2,317
Basic net income per share attributable to the Company (in dollars per share)	$ 2.31	$ 2.15	$ 5.17	$ 4.68
Diluted net income per share attributable to the Company (in dollars per share)	$ 2.29	$ 2.13	$ 5.13	$ 4.64

Goodwill and Other Intangible_2

Goodwill and Other Intangibles (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Indefinite-lived intangible assets	$ 0		$ 0		$ 0
Goodwill	17,516,000,000	$ 16,621,000,000	17,516,000,000	$ 16,621,000,000	$ 17,231,000,000	$ 16,251,000,000
Aggregate amortization expense	89,000,000	$ 87,000,000	179,000,000	$ 172,000,000
Risk and Insurance Services
Segment Reporting Information [Line Items]
Goodwill expected to be tax deductible	254,000,000		254,000,000
Goodwill	13,400,000,000		13,400,000,000
Consulting
Segment Reporting Information [Line Items]
Goodwill expected to be tax deductible	81,000,000		81,000,000
Goodwill	$ 4,100,000,000		$ 4,100,000,000

Goodwill and Other Intangible_3

Goodwill and Other Intangibles (Changes in the Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Goodwill [Roll Forward]
Balance at January 1,	$ 17,231	$ 16,251
Goodwill acquired	430	236
Other adjustments	(145)	134
Balance at June 30,	$ 17,516	$ 16,621

Goodwill and Other Intangible_4

Goodwill and Other Intangibles (Amortized Intangible Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Gross Cost	$ 4,874	$ 4,728
Accumulated Amortization	2,236	2,098
Net Carrying Amount	2,638	2,630
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross Cost	4,498	4,337
Accumulated Amortization	1,905	1,761
Net Carrying Amount	2,593	2,576
Other
Finite-Lived Intangible Assets [Line Items]
Gross Cost	376	391
Accumulated Amortization	331	337
Net Carrying Amount	$ 45	$ 54

Goodwill And Other Intangible_5

Goodwill And Other Intangibles (Estimated Future Aggregate Amortization Expense) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
2024 (excludes amortization through June 30, 2024)	$ 174
2025	322
2026	301
2027	293
2028	271
Subsequent years	1,277
Net Carrying Amount	$ 2,638	$ 2,630

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of investment	$ 276		$ 276		$ 266
Equity securities	19		19		16
Gain (loss) on equity securities			2	$ 1
Equity investments without readily determinable market value	20		20		20
Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Proceeds from contingent purchase consideration, asset			1
Private Insurance and Consulting
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of investment	73		73		63
Private Equity Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of investment	203		203		$ 203
Equity method investment income (loss)	1	$ 3		$ 6
Commitments for potential future investments	$ 114		$ 114
Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revenue target period (in years)			2 years	2 years
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revenue target period (in years)			4 years	4 years

Fair Value Measurements (Assets

Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financial instruments owned:
Exchange traded equity securities	$ 19	$ 16
Fair Value, Measurements, Recurring
Financial instruments owned:
Total assets measured at fair value	544	790
Fiduciary Assets:
Total fiduciary assets measured at fair value	65	180
Liabilities:
Total liabilities measured at fair value	121	252
Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Financial instruments owned:
Total assets measured at fair value	544	789
Fiduciary Assets:
Total fiduciary assets measured at fair value	65	180
Liabilities:
Total liabilities measured at fair value	0	0
Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Financial instruments owned:
Total assets measured at fair value	0	0
Fiduciary Assets:
Total fiduciary assets measured at fair value	0	0
Liabilities:
Total liabilities measured at fair value	0	0
Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Financial instruments owned:
Total assets measured at fair value	0	1
Fiduciary Assets:
Total fiduciary assets measured at fair value	0	0
Liabilities:
Total liabilities measured at fair value	121	252
Money market funds | Fair Value, Measurements, Recurring
Fiduciary Assets:
Total fiduciary assets measured at fair value	65	180
Money market funds | Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Fiduciary Assets:
Total fiduciary assets measured at fair value	65	180
Money market funds | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Fiduciary Assets:
Total fiduciary assets measured at fair value	0	0
Money market funds | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fiduciary Assets:
Total fiduciary assets measured at fair value	0	0
Other Assets | Fair Value, Measurements, Recurring
Financial instruments owned:
Exchange traded equity securities	8	5
Mutual funds	182	178
Other Assets | Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Financial instruments owned:
Exchange traded equity securities	8	5
Mutual funds	182	178
Other Assets | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Financial instruments owned:
Exchange traded equity securities	0	0
Mutual funds	0	0
Other Assets | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Financial instruments owned:
Exchange traded equity securities	0	0
Mutual funds	0	0
Money market funds | Fair Value, Measurements, Recurring
Financial instruments owned:
Money market funds	354	606
Money market funds | Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Financial instruments owned:
Money market funds	354	606
Money market funds | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Financial instruments owned:
Money market funds	0	0
Money market funds | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Financial instruments owned:
Money market funds	0	0
Contingent purchase consideration assets | Fair Value, Measurements, Recurring
Financial instruments owned:
Contingent purchase consideration assets	0	1
Contingent purchase consideration assets | Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Financial instruments owned:
Contingent purchase consideration assets	0	0
Contingent purchase consideration assets | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Financial instruments owned:
Contingent purchase consideration assets	0	0
Contingent purchase consideration assets | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Financial instruments owned:
Contingent purchase consideration assets	0	1
Contingent purchase consideration liabilities | Fair Value, Measurements, Recurring
Liabilities:
Contingent purchase consideration liabilities	121	252
Contingent purchase consideration liabilities | Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Liabilities:
Contingent purchase consideration liabilities	0	0
Contingent purchase consideration liabilities | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Liabilities:
Contingent purchase consideration liabilities	0	0
Contingent purchase consideration liabilities | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Liabilities:
Contingent purchase consideration liabilities	$ 121	$ 252

Fair Value Measurements (Change

Fair Value Measurements (Changes in Fair Value Of Level 3 Liabilities Representing Acquisition Related Contingent Consideration) (Details) - Contingent Consideration - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 242	$ 383	$ 252	$ 377
Net additions	4	4	17	4
Payments	(135)	(174)	(161)	(175)
Revaluation impact	9	10	15	17
Other	1	0	(2)	0
Balance at end of period	$ 121	$ 223	$ 121	$ 223

Derivatives (Details)

Derivatives (Details) - 6 months ended Jun. 30, 2024 $ in Millions, € in Billions	USD ($)	EUR (€)
Derivative [Line Items]
Net investment hedge, threshold percentage of the equity balance	80%
Decrease in net investment hedges | $	$ 47
Net Investment Hedging
Derivative [Line Items]
Derivative, notional amount | €		€ 1.1

Leases (Narrative) (Details)

Leases (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Lessee, Lease, Description [Line Items]
ROU assets impairment loss	$ 1	$ 5	$ 2	$ 13
Lessee, operating lease, lease not yet commenced, amount	$ 25		$ 25
Minimum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract (in years)	10 years		10 years
Maximum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract (in years)	25 years		25 years

Leases (Lease Cost and Addition

Leases (Lease Cost and Additional Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Leases [Abstract]
Operating lease cost	$ 81	$ 81	$ 163	$ 161
Short-term lease cost	2	2	3	3
Variable lease cost	28	26	54	63
Sublease income	(5)	(2)	(8)	(6)
Net lease cost	$ 106	$ 107	212	221
Operating cash outflows from operating leases			183	189
Right of use assets obtained in exchange for new operating lease liabilities			$ 85	$ 121
Weighted average remaining lease term – real estate	7 years 9 months 18 days	8 years 3 months 18 days	7 years 9 months 18 days	8 years 3 months 18 days
Weighted average discount rate – real estate leases	3.58%	3.21%	3.58%	3.21%

Leases (Future Minimum Payments

Leases (Future Minimum Payments for Operating Leases) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Leases [Abstract]
2024 (excludes payments through June 30, 2024)	$ 182
2025	355
2026	327
2027	289
2028	214
2029	170
Subsequent years	616
Total future lease payments	2,153
Less: Imputed interest	(263)
Total	1,890
Current lease liabilities	304	$ 312
Long-term lease liabilities	$ 1,586	$ 1,661

Retirement Benefits (Schedule o

Retirement Benefits (Schedule of Weighted Average Actuarial Assumptions Utilized to Calculate the Net Periodic Benefit Costs) (Details) - Pension Benefits	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Weighted average assumptions:
Expected return on plan assets	5.44%	5.31%
Discount rate	4.95%	5.16%
United States
Weighted average assumptions:
Rate of compensation increase	0%	0%
Foreign Plan
Weighted average assumptions:
Rate of compensation increase	3.16%	3.16%

Retirement Benefits (Narrative)

Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Dec. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer		$ 27	$ 26	$ 51	$ 47
Estimated future employer contributions in current fiscal year		43		43
United States
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized		48	44	97	88
United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized		$ 39	$ 38	$ 91	$ 81
United Kingdom | Defined Benefit Plan Assets Benchmark | Geographic Concentration Risk
Defined Benefit Plan Disclosure [Line Items]
Concentration risk percentage	79%
Equity Funds | United States
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage		50%		50%
Actual asset allocation percentage of equity		51%		51%
Equity Funds | United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage		14%		14%
Actual asset allocation percentage of equity		14%		14%
Fixed Income Funds | United States
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage		50%		50%
Actual asset allocation percentage of equity		49%		49%
Fixed Income Funds | United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage		86%		86%
Actual asset allocation percentage of equity		86%		86%

Retirement Benefits (Schedule_2

Retirement Benefits (Schedule of Defined Benefit Plan Net Periodic Benefit Cost Combined U.S. and Significant Non-U.S. Plans) (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6	$ 5	$ 12	$ 11
Interest cost	144	150	288	298
Expected return on plan assets	(216)	(215)	(435)	(427)
Amortization of prior service (credit) cost	1	0	1	0
Recognized actuarial loss	7	5	15	11
Net benefit credit	(58)	(55)	(119)	(107)
United States
Defined Benefit Plan Disclosure [Line Items]
Interest cost	63	65	125	130
Expected return on plan assets	(75)	(77)	(151)	(155)
Recognized actuarial loss	5	4	10	9
Net benefit credit	(7)	(8)	(16)	(16)
Foreign Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	5	12	11
Interest cost	81	85	163	168
Expected return on plan assets	(141)	(138)	(284)	(272)
Amortization of prior service (credit) cost	1	0	1	0
Recognized actuarial loss	2	1	5	2
Net benefit credit	$ (51)	$ (47)	$ (103)	$ (91)

Retirement Benefits (Schedule_3

Retirement Benefits (Schedule of Defined Benefit Plan Net Periodic Benefit Cost Amounts Recorded in Consolidated Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Compensation and benefits expense	$ (1,642)	$ (1,457)	$ (3,567)	$ (3,183)
Other net benefit credits	(66)	(60)	(133)	(118)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Compensation and benefits expense	6	5	12	11
Other net benefit credits	(64)	(60)	(131)	(118)
Net benefit credit	$ (58)	$ (55)	$ (119)	$ (107)

Debt (Schedule of Outstanding D

Debt (Schedule of Outstanding Debt) (Details) - USD ($)	Jun. 30, 2024	Feb. 29, 2024	Dec. 31, 2023	Sep. 30, 2023	Mar. 31, 2023
Debt Instrument [Line Items]
Commercial paper	$ 749,000,000		$ 0
Current portion of long-term debt	518,000,000		1,619,000,000
Short-term debt	1,267,000,000		1,619,000,000
Long-term debt	12,796,000,000		13,463,000,000
Long-term debt, net	12,278,000,000		11,844,000,000
Senior notes – 3.50% due 2024
Debt Instrument [Line Items]
Long-term debt	$ 0		600,000,000
Interest rate	3.50%
Senior notes – 3.875% due 2024
Debt Instrument [Line Items]
Long-term debt	$ 0		1,000,000,000
Interest rate	3.875%
Senior notes – 3.50% due 2025
Debt Instrument [Line Items]
Long-term debt	$ 500,000,000		499,000,000
Interest rate	3.50%
Senior notes – 1.349% due 2026
Debt Instrument [Line Items]
Long-term debt	$ 593,000,000		617,000,000
Interest rate	1.349%
Senior notes – 3.75% due 2026
Debt Instrument [Line Items]
Long-term debt	$ 599,000,000		599,000,000
Interest rate	3.75%
Senior notes – 4.375% due 2029
Debt Instrument [Line Items]
Long-term debt	$ 1,499,000,000		1,499,000,000
Interest rate	4.375%
Senior notes – 1.979% due 2030
Debt Instrument [Line Items]
Long-term debt	$ 578,000,000		601,000,000
Interest rate	1.979%
Senior notes – 2.25% due 2030
Debt Instrument [Line Items]
Long-term debt	$ 742,000,000		741,000,000
Interest rate	2.25%
Senior notes – 2.375% due 2031
Debt Instrument [Line Items]
Long-term debt	$ 397,000,000		397,000,000
Interest rate	2.375%
Senior notes – 5.750% due 2032
Debt Instrument [Line Items]
Long-term debt	$ 493,000,000		493,000,000
Interest rate	5.75%
Senior notes – 5.875% due 2033
Debt Instrument [Line Items]
Long-term debt	$ 298,000,000		298,000,000
Interest rate	5.875%
Senior notes – 5.400% due 2033
Debt Instrument [Line Items]
Long-term debt	$ 592,000,000		592,000,000
Interest rate	5.40%			5.40%
Senior notes – 5.150% due 2034
Debt Instrument [Line Items]
Long-term debt	$ 495,000,000		0
Interest rate	5.15%	5.15%
Senior notes – 4.75% due 2039
Debt Instrument [Line Items]
Long-term debt	$ 496,000,000		496,000,000
Interest rate	4.75%
Senior notes – 4.35% due 2047
Debt Instrument [Line Items]
Long-term debt	$ 494,000,000		494,000,000
Interest rate	4.35%
Senior notes – 4.20% due 2048
Debt Instrument [Line Items]
Long-term debt	$ 593,000,000		593,000,000
Interest rate	4.20%
Senior notes – 4.90% due 2049
Debt Instrument [Line Items]
Long-term debt	$ 1,239,000,000		1,239,000,000
Interest rate	4.90%
Senior notes – 2.90% due 2051
Debt Instrument [Line Items]
Long-term debt	$ 346,000,000		346,000,000
Interest rate	2.90%
Senior notes – 6.25% due 2052
Debt Instrument [Line Items]
Long-term debt	$ 491,000,000		491,000,000
Interest rate	6.25%
Senior notes – 5.450% due 2053
Debt Instrument [Line Items]
Long-term debt	$ 591,000,000		591,000,000
Interest rate	5.45%				5.45%
Senior notes – 5.700% due 2053
Debt Instrument [Line Items]
Long-term debt	$ 988,000,000		988,000,000
Interest rate	5.70%
Senior notes – $5.450% due 2054
Debt Instrument [Line Items]
Long-term debt	$ 493,000,000		0
Interest rate	5.45%	5.45%
Mortgage – 5.70% due 2035
Debt Instrument [Line Items]
Long-term debt	$ 276,000,000		284,000,000
Interest rate	5.70%
Other
Debt Instrument [Line Items]
Long-term debt	$ 3,000,000		$ 5,000,000

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($)	1 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Oct. 31, 2023	Feb. 29, 2024	Dec. 31, 2023	Nov. 30, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Oct. 31, 2022	Sep. 30, 2022
Debt Instrument [Line Items]
Commercial paper outstanding	$ 749,000,000				$ 0
Other Debt Facilities
Debt Instrument [Line Items]
Revolving credit facility, amount outstanding	0				0
Other credit and overdraft facilities	118,000,000				113,000,000
Letters of credit	$ 143,000,000				139,000,000
Senior notes – 3.50% due 2024
Debt Instrument [Line Items]
Interest rate	3.50%
3.875% Senior Debt Obligations October 2024
Debt Instrument [Line Items]
Interest rate		3.875%
Senior notes – 5.150% due 2034
Debt Instrument [Line Items]
Interest rate	5.15%			5.15%
Senior notes – $5.450% due 2054
Debt Instrument [Line Items]
Interest rate	5.45%			5.45%
4.05% Senior Debt Obligations October 2023
Debt Instrument [Line Items]
Interest rate			4.05%
Senior notes – 5.400% due 2033
Debt Instrument [Line Items]
Interest rate	5.40%						5.40%
5.700% Senior Debt Obligations Due 2053
Debt Instrument [Line Items]
Interest rate							5.70%
Senior notes – 5.450% due 2053
Debt Instrument [Line Items]
Interest rate	5.45%								5.45%
Senior Notes | Senior notes – 3.50% due 2024
Debt Instrument [Line Items]
Repayments of debt	$ 600,000,000
Senior Notes | 3.875% Senior Debt Obligations October 2024
Debt Instrument [Line Items]
Repayments of debt		$ 1,000,000,000
Senior Notes | Senior notes – 5.150% due 2034
Debt Instrument [Line Items]
Debt instrument face amount				$ 500,000,000
Senior Notes | Senior notes – $5.450% due 2054
Debt Instrument [Line Items]
Debt instrument face amount				$ 500,000,000
Senior Notes | 4.05% Senior Debt Obligations October 2023
Debt Instrument [Line Items]
Repayments of debt			$ 250,000,000
Senior Notes | Senior notes – 5.400% due 2033
Debt Instrument [Line Items]
Debt instrument face amount							$ 600,000,000
Senior Notes | 5.700% Senior Debt Obligations Due 2053
Debt Instrument [Line Items]
Debt instrument face amount							1,000,000,000
Senior Notes | Senior notes – 5.450% due 2053
Debt Instrument [Line Items]
Debt instrument face amount									$ 600,000,000
Revolving credit facility
Debt Instrument [Line Items]
Debt instrument, term			5 years
Revolving credit facility, borrowing capacity			$ 3,500,000,000
Revolving credit facility | New Facility
Debt Instrument [Line Items]
Revolving credit facility, borrowing capacity							$ 2,800,000,000
Revolving credit facility, amount outstanding	$ 0				$ 0
Revolving credit facility | Uncommitted Credit Facility
Debt Instrument [Line Items]
Debt instrument, term			1 year
Revolving credit facility, amount outstanding								$ 200,000,000
Debt, weighted average interest rate								5.50%
Commercial paper
Debt Instrument [Line Items]
Short-term debt			$ 2,800,000,000			$ 3,500,000,000				$ 2,800,000,000	$ 2,000,000,000
Effective interest rate (percent)	5.498%

Debt (Estimated Fair Value of S

Debt (Estimated Fair Value of Significant Financial Instruments) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	$ 1,267	$ 1,619
Long-term debt	12,278	11,844
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	1,261	1,610
Long-term debt	$ 11,707	$ 11,723

Restructuring Costs (Narrative)

Restructuring Costs (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]
Costs incurred	$ 44	$ 65	$ 86	$ 118	$ 301
Severance and Lease Exit Charges
Restructuring Cost and Reserve [Line Items]
Costs incurred	$ 30		$ 60

Restructuring Costs (Restructur

Restructuring Costs (Restructuring and Related Costs Incurred) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]
Total	$ 44	$ 65	$ 86	$ 118	$ 301
Corporate
Restructuring Cost and Reserve [Line Items]
Total	10	27	19	39
Risk and Insurance Services
Restructuring Cost and Reserve [Line Items]
Total	29	31	51	63
Consulting
Restructuring Cost and Reserve [Line Items]
Total	$ 5	$ 7	$ 16	$ 16

Restructuring Costs (Restruct_2

Restructuring Costs (Restructuring Activities) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Restructuring Reserve [Roll Forward]
Liability at beginning of period			$ 130	$ 146	$ 146
Restructuring charges	$ 44	$ 65	86	118	301
Cash payments			(153)		(271)
Non-cash charges			(3)		(46)
Liability at end of period	60		60		130
Severance
Restructuring Reserve [Roll Forward]
Liability at beginning of period			89	88	88
Restructuring charges			42		148
Cash payments			(102)		(147)
Non-cash charges			0		0
Liability at end of period	29		29		89
Real Estate Related Costs
Restructuring Reserve [Roll Forward]
Liability at beginning of period			39	56	56
Restructuring charges			21		96
Cash payments			(26)		(69)
Non-cash charges			(3)		(44)
Liability at end of period	31		31		39
Information Technology
Restructuring Reserve [Roll Forward]
Liability at beginning of period			0	0	0
Restructuring charges			11		15
Cash payments			(11)		(13)
Non-cash charges			0		(2)
Liability at end of period	0		0		0
Consulting and Other Outside Services
Restructuring Reserve [Roll Forward]
Liability at beginning of period			2	$ 2	2
Restructuring charges			12		42
Cash payments			(14)		(42)
Non-cash charges			0		0
Liability at end of period	$ 0		$ 0		$ 2

Common Stock (Details)

Common Stock (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended					6 Months Ended
	Jul. 18, 2024	May 31, 2024	Mar. 31, 2024	Feb. 29, 2024	Jan. 31, 2024	Jun. 30, 2024	Jun. 30, 2023
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased (in shares)							3.5
Purchase of treasury shares						$ 600	$ 600
Stock-based compensation, shares issued during period (in shares)						2.9	2.8
Dividend per share (in dollars per share)			$ 0.710		$ 0.710
Dividends, per share, cash paid (in dollars per share)		$ 0.710		$ 0.710
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Dividend per share (in dollars per share)	$ 0.815
Dividends, per share, payable (in dollars per share)	$ 0.815
Common Stock
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased (in shares)						3
Stock repurchase program, remaining authorized repurchase amount						$ 2,600

Segment Information (Selected I

Segment Information (Selected Information and Details for MMC's Operating Segments) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Jan. 01, 2024	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Revenue		$ 6,221	$ 5,876	$ 12,694	$ 11,800
Operating Income/(Loss)		1,642	1,457	3,567	3,183
Discontinued Operations, Disposed of by Sale | U.S. Health And Benefits And U.K Pension Administration Businesses
Segment Reporting Information [Line Items]
Net gain includes in revenue consolidated statements of income	$ 21
Total Segments
Segment Reporting Information [Line Items]
Revenue		6,238	5,894	12,725	11,831
Operating Income/(Loss)		1,707	1,545	3,704	3,351
Total Segments | Discontinued Operations, Disposed of by Sale | U.S. Health And Benefits And U.K Pension Administration Businesses
Segment Reporting Information [Line Items]
Net gain includes in revenue consolidated statements of income				21
Total Segments | Risk and Insurance Services
Segment Reporting Information [Line Items]
Revenue		4,022	3,722	8,295	7,628
Operating Income/(Loss)		1,297	1,157	2,862	2,552
Interest on fiduciary funds		125	108	247	199
Equity method investment income (loss)		10	12	10	11
Total Segments | Consulting
Segment Reporting Information [Line Items]
Revenue		2,216	2,172	4,430	4,203
Operating Income/(Loss)		410	388	842	799
Corporate/Eliminations
Segment Reporting Information [Line Items]
Revenue		(17)	(18)	(31)	(31)
Operating Income/(Loss)		(65)	(88)	(137)	(168)
Intersegment Eliminations | Risk and Insurance Services
Segment Reporting Information [Line Items]
Revenue		4	5	5	5
Intersegment Eliminations | Consulting
Segment Reporting Information [Line Items]
Revenue		$ 13	$ 13	$ 26	$ 26

Segment Information (Details of

Segment Information (Details of Operating Segment Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Revenue	$ 6,221	$ 5,876	$ 12,694	$ 11,800
Total Segments
Segment Reporting Information [Line Items]
Revenue	6,238	5,894	12,725	11,831
Total Segments | Risk and Insurance Services
Segment Reporting Information [Line Items]
Revenue	4,022	3,722	8,295	7,628
Total Segments | Risk and Insurance Services | Marsh
Segment Reporting Information [Line Items]
Revenue	3,342	3,103	6,423	5,903
Total Segments | Risk and Insurance Services | Guy Carpenter
Segment Reporting Information [Line Items]
Revenue	680	619	1,872	1,725
Total Segments | Consulting
Segment Reporting Information [Line Items]
Revenue	2,216	2,172	4,430	4,203
Total Segments | Consulting | Mercer
Segment Reporting Information [Line Items]
Revenue	1,379	1,374	2,804	2,718
Total Segments | Consulting | Oliver Wyman Group
Segment Reporting Information [Line Items]
Revenue	837	798	1,626	1,485
Corporate/Eliminations
Segment Reporting Information [Line Items]
Revenue	$ (17)	$ (18)	$ (31)	$ (31)