Arthur J. Gallagher & Co. (AJG) 10-Q 26 Jul 24 2024 Q2 Quarterly report Financial data

Cover Page

Cover Page	6 Months Ended
	Jun. 30, 2024 shares
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Period End Date	Jun. 30, 2024
Document Fiscal Period Focus	Q2
Entity Interactive Data Current	Yes
Entity Central Index Key	0000354190
Current Fiscal Year End Date	--12-31
Entity Registrant Name	ARTHUR J. GALLAGHER & CO.
Entity File Number	1-09761
Document Transition Report	false
Entity Tax Identification Number	36-2151613
Entity Incorporation, State or Country Code	DE
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Address, Address Line One	2850 Golf Road
Entity Address, City or Town	Rolling Meadows
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60008
City Area Code	630
Local Phone Number	773-3800
Entity Shell Company	false
Trading Symbol	AJG
Security Exchange Name	NYSE
Title of 12(b) Security	Common Stock, par value $1.00 per share
Entity Common Stock, Shares Outstanding	219,100,000
Document Quarterly Report	true

Consolidated Statement of Earni

Consolidated Statement of Earnings - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenues before reimbursements	$ 2,736	$ 2,406.9	$ 5,954.1	$ 5,079.8
Reimbursements	39.4	35	78	68.2
Total revenues	2,775.4	2,441.9	6,032.1	5,148
Compensation	1,620.1	1,413	3,346	2,828.5
Operating	425.6	433.6	861.3	816.1
Reimbursements	39.4	35	78	68.2
Interest	94.3	77.8	186.5	145.7
Depreciation	40.8	40.8	86.2	78.5
Amortization	170.8	134.9	333.1	256.6
Change in estimated acquisition earnout payables	18.8	9.4	2.7	51.2
Total expenses	2,409.8	2,144.5	4,893.8	4,244.8
Earnings before income taxes	365.6	297.4	1,138.3	903.2
Provision for income taxes	80.2	61.6	240.2	180.8
Net earnings	285.4	235.8	898.1	722.4
Net earnings attributable to noncontrolling interests	2	1.3	6.3	1.4
Net earnings attributable to controlling interests	$ 283.4	$ 234.5	$ 891.8	$ 721
Basic net earnings per share	$ 1.3	$ 1.09	$ 4.09	$ 3.37
Diluted net earnings per share	1.27	1.07	4.01	3.31
Dividends declared per common share	$ 0.6	$ 0.55	$ 1.2	$ 1.1
Commissions [Member]
Revenues before reimbursements	$ 1,661.8	$ 1,410.4	$ 3,655.4	$ 3,157.8
Broker Fees [Member]
Revenues before reimbursements	827.1	790.5	1,778.3	1,496.2
Supplemental Revenue [Member]
Revenues before reimbursements	88.7	71.2	182.6	152.8
Contingent Revenue [Member]
Revenues before reimbursements	59.8	54.2	145.8	126
Investment Income [Member]
Revenues before reimbursements	$ 98.6	$ 80.6	$ 192	$ 147

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Earnings - 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 earnings	$ 285.4	$ 235.8	$ 898.1	$ 722.4
Change in pension liability, net of taxes	(0.1)	0.7	0.2	1.5
Foreign currency translation, net of taxes	11.3	193.5	(144.5)	226.8
Change in fair value of derivative investments, net of taxes	(1.4)	24.3	(2.8)	29.2
Comprehensive earnings	295.2	454.3	751	979.9
Comprehensive earnings attributable to noncontrolling interests	2.1	1.6	6.4	1.6
Comprehensive earnings attributable to controlling interests	$ 293.1	$ 452.7	$ 744.6	$ 978.3

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Cash and cash equivalents	$ 1,415.3	$ 971.5
Fiduciary assets (includes fiduciary cash of $5,422.5 and $5,571.8 in 2023)	37,316.9	26,907.9
Accounts receivable, net	4,178.3	3,786.6
Other current assets	403	450.1
Total current assets	43,313.5	32,116.1
Fixed assets - net	655.3	726.4
Deferred income taxes (includes tax credit carryforwards of $805.1 in 2024 and $867.4 in 2023)	1,040.1	1,132.3
Other noncurrent assets	1,311.6	1,131.8
Right-of-use assets	382.3	400.3
Goodwill	11,915.5	11,475.6
Amortizable intangible assets - net	4,389.4	4,633.3
Total assets	63,007.7	51,615.8
Fiduciary liabilities	37,316.9	26,907.9
Accrued compensation and other current liabilities	3,107.8	2,553.1
Deferred revenue - current	697.1	644.7
Premium financing debt	207.8	289
Corporate related borrowings - current	280	670
Total current liabilities	41,609.6	31,064.7
Corporate related borrowings - noncurrent	7,790.9	7,006
Deferred revenue - noncurrent	65.8	61.5
Lease liabilities - noncurrent	335.2	352.2
Other noncurrent liabilities	1,606.9	2,316.1
Total liabilities	51,408.4	40,800.5
Stockholders' equity:
Common stock - issued and outstanding 219.1 shares in 2024 and 216.7 shares in 2023	219.1	216.7
Capital in excess of par value	7,611.4	7,297.8
Retained earnings	4,681.2	4,052.9
Accumulated other comprehensive loss	(939.2)	(792.1)
Stockholders' equity attributable to controlling interests	11,572.5	10,775.3
Stockholders' equity attributable to noncontrolling interests	26.8	40
Total stockholders' equity	11,599.3	10,815.3
Total liabilities and stockholders' equity	$ 63,007.7	$ 51,615.8

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - USD ($) shares in Millions, $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Fiduciary cash	$ 5,422.5	$ 5,571.8
Deferred income tax credit carryforwards	$ 805.1	$ 867.4
Common stock - issued shares	219.1	216.7
Common stock - outstanding shares	219.1	216.7

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities:
Net earnings	$ 898.1	$ 722.4
Adjustments to reconcile net earnings to net cash provided by operating activities:
Net gain on investments and other	(1.8)	(4.1)
Depreciation and amortization	419.3	335.1
Change in estimated acquisition earnout payables	2.7	51.2
Amortization of deferred compensation and restricted stock	58.1	48.5
Stock-based and other noncash compensation expense	21.1	11.9
Payments on acquisition earnouts in excess of original estimates	(23.3)	(57.5)
Provision for deferred income taxes	5.6	(0.9)
Effect of changes in foreign exchange rates	0.6	11
Net change in accounts receivable, net	(469.2)	(732.3)
Net change in deferred revenue	55.3	78.8
Net change in other current assets	2.7	(29.9)
Net change in accrued compensation and other accrued liabilities	(94.5)	15
Net change in income taxes payable	0.6	14.9
Net change in other noncurrent assets and liabilities	33.5	(23.2)
Net cash provided by operating activities	908.8	440.9
Cash flows from investing activities:
Capital expenditures	(61.5)	(88.8)
Cash paid for acquisitions, net of cash and restricted cash acquired	(518.6)	(1,049.5)
Net proceeds from sales of operations/books of business	1.7	4.8
Net funding of investment transactions	0.8	4.5
Net funding of premium finance loans	78	63.9
Net cash used by investing activities	(499.6)	(1,065.1)
Cash flows from financing activities:
Payments on acquisition earnouts	(104.4)	(72.5)
Proceeds from issuance of common stock	93.5	66
Payments to noncontrolling interests	(4.1)	(1.2)
Dividends paid	(262)	(235.9)
Net change in fiduciary assets and liabilities	(103.1)	1,727
Net borrowings on premium financing debt facility	(73.1)	(53.2)
Borrowings on line of credit facility	1,663.2	2,125
Repayments on line of credit facility	(1,826.9)	(1,690)
Net borrowings of corporate related long-term debt	567.5	643.7
Debt acquisition costs	(8.4)	(8.6)
Settlements on terminated interest rate swaps	(1.4)	60
Net cash (used) provided by financing activities	(59.2)	2,560.3
Effect of changes in foreign exchange rates on cash, cash equivalents, restricted cash and fiduciary cash	(55.5)	41.9
Net increase in cash, cash equivalents, restricted cash and fiduciary cash	294.5	1,978
Cash, cash equivalents, restricted cash and fiduciary cash at beginning of period	6,543.3	4,964.2
Cash, cash equivalents, restricted cash and fiduciary cash at end of period	$ 6,837.8	$ 6,942.2

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Capital in Excess of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]
Beginning balance at Dec. 31, 2022	$ 9,190.2	$ 211.9	$ 6,509.9	$ 3,562.2	$ (1,140.4)	$ 46.6
Beginning balance (in shares) at Dec. 31, 2022		211.9
Net earnings	486.6			486.5		0.1
Net purchase of subsidiary shares from noncontrolling interests	(5.4)					(5.4)
Dividends paid to noncontrolling interests	(0.7)					(0.7)
Net change in pension asset/liability, net of taxes	0.8				0.8
Foreign currency translation	33.2				33.3	(0.1)
Change in fair value of derivative instruments, net of taxes	4.9				4.9
Compensation expense related to stock option plan grants	7.7		7.7
Common stock issued in: purchase transactions	186.5	$ 1	185.5
Common stock issued in: purchase transactions (in shares)		1
Stock option plans	21.2	$ 0.5	20.7
Stock option plans (in shares)		0.5
Employee stock purchase plan	9.1	$ 0.1	9
Employee stock purchase plan (in shares)		0.1
Shares issued to benefit plans	84.6	$ 0.4	84.2
Shares issued to benefit plans (in shares)		0.4
Deferred compensation and restricted stock	(41.9)	$ 0.3	(42.2)
Deferred compensation and restricted (in shares)		0.3
Cash dividends declared on common stock	(118.5)			(118.5)
Ending balance at Mar. 31, 2023	9,858.3	$ 214.2	6,774.8	3,930.2	(1,101.4)	40.5
Ending balance, (in shares) at Mar. 31, 2023		214.2
Beginning balance at Dec. 31, 2022	9,190.2	$ 211.9	6,509.9	3,562.2	(1,140.4)	46.6
Beginning balance (in shares) at Dec. 31, 2022		211.9
Net earnings	722.4
Net change in pension asset/liability, net of taxes	1.5
Change in fair value of derivative instruments, net of taxes	29.2
Compensation expense related to stock option plan grants	15.5
Ending balance at Jun. 30, 2023	10,440	$ 215.5	7,018	4,045.1	(882.9)	44.3
Ending balance, (in shares) at Jun. 30, 2023		215.5
Beginning balance at Mar. 31, 2023	9,858.3	$ 214.2	6,774.8	3,930.2	(1,101.4)	40.5
Beginning balance (in shares) at Mar. 31, 2023		214.2
Net earnings	235.8			234.5		1.3
Net purchase of subsidiary shares from noncontrolling interests	2.7					2.7
Dividends paid to noncontrolling interests	(0.5)					(0.5)
Net change in pension asset/liability, net of taxes	0.7				0.7
Foreign currency translation	193.8				193.5	0.3
Change in fair value of derivative instruments, net of taxes	24.3				24.3
Compensation expense related to stock option plan grants	7.8		7.8
Common stock issued in: purchase transactions	178.6	$ 0.8	177.8
Common stock issued in: purchase transactions (in shares)		0.8
Stock option plans	22.8	$ 0.4	22.4
Stock option plans (in shares)		0.4
Employee stock purchase plan	13	$ 0.1	12.9
Employee stock purchase plan (in shares)		0.1
Deferred compensation and restricted stock	22.3		22.3
Cash dividends declared on common stock	(119.6)			(119.6)
Ending balance at Jun. 30, 2023	10,440	$ 215.5	7,018	4,045.1	(882.9)	44.3
Ending balance, (in shares) at Jun. 30, 2023		215.5
Beginning balance at Dec. 31, 2023	$ 10,815.3	$ 216.7	7,297.8	4,052.9	(792.1)	40
Beginning balance (in shares) at Dec. 31, 2023	216.7	216.7
Net earnings	$ 612.7			608.4		4.3
Net purchase of subsidiary shares from noncontrolling interests	(0.3)					(0.3)
Dividends paid to noncontrolling interests	(0.6)					(0.6)
Net change in pension asset/liability, net of taxes	0.3				0.3
Foreign currency translation	(155.8)				(155.8)
Change in fair value of derivative instruments, net of taxes	(1.4)				(1.4)
Compensation expense related to stock option plan grants	15.1		15.1
Common stock issued in: purchase transactions	88.3	$ 0.4	87.9
Common stock issued in: purchase transactions (in shares)		0.4
Stock option plans	39.9	$ 0.6	39.3
Stock option plans (in shares)		0.6
Employee stock purchase plan	12.2	$ 0.1	12.1
Employee stock purchase plan (in shares)		0.1
Shares issued to benefit plans	98.5	$ 0.4	98.1
Shares issued to benefit plans (in shares)		0.4
Deferred compensation and restricted stock	(48)	$ 0.3	(48.3)
Deferred compensation and restricted (in shares)		0.3
Cash dividends declared on common stock	(132)			(132)
Ending balance at Mar. 31, 2024	11,344.2	$ 218.5	7,502	4,529.3	(949)	43.4
Ending balance, (in shares) at Mar. 31, 2024		218.5
Beginning balance at Dec. 31, 2023	$ 10,815.3	$ 216.7	7,297.8	4,052.9	(792.1)	40
Beginning balance (in shares) at Dec. 31, 2023	216.7	216.7
Net earnings	$ 898.1
Net change in pension asset/liability, net of taxes	0.2
Change in fair value of derivative instruments, net of taxes	(2.8)
Compensation expense related to stock option plan grants	$ 25.6
Stock option plans (in shares)	1
Ending balance at Jun. 30, 2024	$ 11,599.3	$ 219.1	7,611.4	4,681.2	(939.2)	26.8
Ending balance, (in shares) at Jun. 30, 2024	219.1	219.1
Beginning balance at Mar. 31, 2024	$ 11,344.2	$ 218.5	7,502	4,529.3	(949)	43.4
Beginning balance (in shares) at Mar. 31, 2024		218.5
Net earnings	285.4			283.4		2
Net purchase of subsidiary shares from noncontrolling interests	(18.4)					(18.4)
Dividends paid to noncontrolling interests	(0.3)					(0.3)
Net change in pension asset/liability, net of taxes	(0.1)				(0.1)
Foreign currency translation	11.4				11.3	0.1
Change in fair value of derivative instruments, net of taxes	(1.4)				(1.4)
Compensation expense related to stock option plan grants	10.5		10.5
Common stock issued in: purchase transactions	45.5	$ 0.2	45.3
Common stock issued in: purchase transactions (in shares)		0.2
Stock option plans	24.8	$ 0.3	24.5
Stock option plans (in shares)		0.3
Employee stock purchase plan	16.5		16.5
Deferred compensation and restricted stock	12.7	$ 0.1	12.6
Deferred compensation and restricted (in shares)		0.1
Cash dividends declared on common stock	(131.5)			(131.5)
Ending balance at Jun. 30, 2024	$ 11,599.3	$ 219.1	$ 7,611.4	$ 4,681.2	$ (939.2)	$ 26.8
Ending balance, (in shares) at Jun. 30, 2024	219.1	219.1

Consolidated Statement of Sto_2

Consolidated Statement of Stockholders' Equity (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023
Statement of Stockholders' Equity [Abstract]
Tax effect on net change in pension asset/liability	$ 0	$ 0.1	$ 0.2	$ 0.2
Net change in fair value of derivative instruments, tax	$ (0.5)	$ (0.4)	$ 8.4	$ 1.3

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ 283.4	$ 234.5	$ 891.8	$ 721

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Jun. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. Summary of Significant Accounting Policies Terms Used in Notes to Consolidated Financial Statements ASC - Accounting Standards Codification. ASU - Accounting Standards Update. FASB - The Financial Accounting Standards Board. GAAP - U.S. generally accepted accounting principles. IRC - Internal Revenue Code. IRS - Internal Revenue Service. Underwriting enterprises - Insurance companies, reinsurance companies and various other forms of risk-taking entities, including intermediaries of underwriting enterprises. Nature of Operations and Basis of Presentation Arthur J. Gallagher & Co. and its subsidiaries, collectively referred to herein as we, our, us, Gallagher or the company, provide insurance and reinsurance brokerage, consulting and third party claims settlement and administration services to both domestic and international entities. We have three reportable segments: brokerage, risk management and corporate. Our brokers, agents and administrators act as intermediaries between underwriting enterprises and our clients. Our brokerage segment operations provide brokerage and consulting services to entities of all types, including commercial, nonprofit, public sector entities, and, to a lesser extent, individuals, in the areas of insurance and reinsurance placements, risk of loss management, and management of employer sponsored benefit programs. Our risk management segment operations provide contract claim settlement, claim administration, loss control services and risk management consulting for commercial, nonprofit, captive and public sector entities, and various other organizations that choose to self-insure property/casualty coverages or choose to use a third‑party claims management organization rather than the claim services provided by underwriting enterprises. The corporate segment reports the financial information related to our debt and other corporate costs, clean energy investments, external acquisition‑related expenses and the impact of foreign currency translation. We do not assume insurance underwriting risk on a net basis, other than with respect to de minimis amounts necessary to provide minimum or regulatory capital to organize captives, pools, specialized underwriters or risk-retention groups. Rather, capital necessary for covering losses is provided by underwriting enterprises. Interest income, premium finance revenues and other income are primarily generated from our premium financing operations, our invested cash and restricted cash we hold on behalf of our clients, as well as clean energy investments. In addition, our share of the net earnings related to partially owned entities that are accounted for using the equity method is included in other income. We are a global insurance brokerage, risk management and consulting services firm, headquartered in Rolling Meadows, Illinois. We provide these services in approximately 130 countries around the world through our owned operations and a network of correspondent brokers and consultants. We have prepared the accompanying unaudited consolidated financial statements pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in annual financial statements have been omitted pursuant to such rules and regulations. The unaudited consolidated financial statements included herein are, in the opinion of management, prepared on a basis consistent with our audited consolidated financial statements for the year ended December 31, 2023, and include all normal recurring adjustments necessary for a fair presentation of the information set forth herein. The quarterly results of operations are not necessarily indicative of the results of operations to be reported for subsequent quarters or the full year. These unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2023. In the preparation of our unaudited consolidated financial statements as of June 30, 2024 , management evaluated all material subsequent events or transactions that occurred after the balance sheet date through the date on which the financial statements were issued, for potential recognition and/or disclosure therein. Use of Estimates The preparation of our unaudited consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. These accounting principles require us to make estimates and assumptions that affect the reported amounts of assets and liabilities and revenues and expenses, and the disclosure of contingent assets and liabilities at the date of our unaudited consolidated financial statements. We periodically evaluate our estimates and assumptions, including those relating to the valuation of goodwill and other intangible assets, right-of-use assets, investments, income taxes, revenue recognition, deferred costs, stock-based compensation, claims handling obligations, retirement plans, litigation and contingencies. We base our estimates on historical experience and various assumptions that we believe to be reasonable based on specific circumstances. Such estimates and assumptions could change in the future as more information becomes known, which could impact the amounts reported and disclosed in the notes herein.

Effect of New Accounting Pronou

Effect of New Accounting Pronouncements	6 Months Ended
	Jun. 30, 2024
Accounting Changes and Error Corrections [Abstract]
Effect of New Accounting Pronouncements	2. Effect of New Accounting Pronouncements Segment Reporting In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires that an entity report segment information in accordance with Topic 280, Segment Reporting. The amendment in the ASU is intended to improve reportable segment disclosure requirements primarily through enhanced disclosures about significant segment expenses. The amendments in this update are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. We are currently evaluating the impact of the new standard on our consolidated financial statements which is expected to result in enhanced disclosures. Income Taxes In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which requires that an entity, on an annual basis, disclose additional income tax information, primarily related to the rate reconciliation and income taxes paid. The amendment in the ASU is intended to enhance the transparency and decision usefulness of income tax disclosures. The amendments in this update are effective for fiscal years beginning after December 15, 2024. We are currently evaluating the impact of the new standard on our consolidated financial statements which is expected to result in enhanced disclosures. Climate Risk Disclosures In March 2024, the SEC issued final climate-related disclosure rules that will require disclosure of material climate-related risks and material direct greenhouse gas emissions from operations owned or controlled (Scope 1) and/or material indirect greenhouse gas emissions from purchased energy consumed in owned or controlled operations (Scope 2). Additionally, the rules require disclosure in the notes to the financial statements of the effects of severe weather events and other natural conditions, subject to certain materiality thresholds. The disclosure requirements were scheduled to begin phasing in for annual reports and registration statements including financial information with respect to annual periods beginning in calendar year 2025. On April 4, 2024, the SEC issued an order staying the rules during the pendency of a number of legal challenges to the rules’ validity. We are continuing to monitor these developments while evaluating the impact of the rules on our consolidated financial statements, which are expected to result in additional disclosures.

Business Combinations

Business Combinations	6 Months Ended
	Jun. 30, 2024
Business Combinations [Abstract]
Business Combinations	3. Business Combinations During the six-month period ended June 30, 2024, we acquired substantially all of the ownership interest or net assets, as applicable, of the following firms in exchange for our common stock and/or cash. These acquisitions have been accounted for using the acquisition method for recording business combinations (in millions, except share data): Total Maximum Common Common Recorded Recorded Potential Name and Effective Shares Share Accrued Escrow Earnout Purchase Earnout Date of Acquisition Issued Value Cash Paid Liability Deposited Payable Price Payable (000s) Ericson Insurance Services, LLC 129 $ 30.1 $ 26.5 $ — $ 3.0 $ 7.0 $ 66.6 $ 10.0 The Rowley Agency, LLC — — 117.2 — 11.0 — 128.2 — OperationsInc, LLC — $ — $ 52.6 $ — $ 2.8 $ 11.0 $ 66.4 $ 20.0 Twenty-one other acquisitions 229 48.8 271.3 2.6 16.8 53.3 392.8 108.5 358 $ 78.9 $ 467.6 $ 2.6 $ 33.6 $ 71.3 $ 654.0 $ 138.5 Common shares issued in connection with acquisitions are valued at closing market prices as of the effective date of the applicable acquisition or on the days when the shares are issued, if purchase consideration is deferred. We record escrow deposits that are returned to us as a result of adjustments to net assets acquired as reductions of goodwill when the escrows are settled. The maximum potential earnout payables disclosed in the foregoing table represent the maximum amount of additional consideration that could be paid pursuant to the terms of the purchase agreement for the applicable acquisition. The amounts recorded as earnout payables, which are primarily based upon the estimated future operating results of the acquired entities over a two- to three-year period subsequent to the acquisition date, are measured at fair value as of the acquisition date and are included on that basis in the recorded purchase price consideration in the foregoing table. We will record subsequent changes in these estimated earnout obligations, including the accretion of discount, in our consolidated statement of earnings when incurred. The fair value of these earnout obligations is generally based on the present value of the expected future payments to be made to the sellers of the acquired entities in accordance with the provisions outlined in the respective purchase agreements, which is a Level 3 fair value measurement (discounted cash flow method of the income approach). In determining fair value, we estimated the acquired entity’s future performance using financial projections developed by management for the acquired entity and market participant assumptions that were derived for revenue growth and/or profitability. Revenue growth rates generally ranged from 5.0 % to 15.0 % for our 2024 acquisitions. We estimated future payments using the earnout formula and performance targets specified in each purchase agreement and the financial projections just described. We then discounted these payments to present value using a risk-adjusted rate that takes into consideration market-based rates of return that reflect the ability of the acquired entity to achieve the targets. The discount rate was 9.0 % for all of our 2024 acquisitions. In some instances, the fair value of these earnout obligations can be based on other valuation methods including the Black-Scholes Option Pricing Method or Monte Carlo Simulation method. Changes in financial projections, market participant assumptions for revenue growth and/or profitability, or the risk-adjusted discount rate, would result in a change in the fair value of recorded earnout obligations. During the three-month periods ended June 30, 2024 and 2023 , we recognized $ 15.0 million and $ 19.8 million, respectively, of expense in our consolidated statement of earnings related to the accretion of the discount recorded for earnout obligations in connection with our acquisitions. During the six-month periods ended June 30, 2024 and 2023 , we recognized $ 33.8 million and $ 39.6 million, respectively, of expense in our consolidated statement of earnings related to the accretion of the discount recorded for earnout obligations in connection with our acquisitions. In addition, during the three-month periods ended June 30, 2024 and 2023 , we recognized $ 3.8 million of expense and $ 10.4 million of income, respectively, related to net adjustments in the estimated fair value of the liability for earnout obligations in connection with revised assumptions due to changes in interest rates, volatility and other assumptions and projections of future performance for 30 and 34 acquisitions, respectively. In addition, during the six-month periods ended June 30, 2024 and 2023 , we recognized $ 31.1 million of income and $ 11.6 million of expense, respectively, related to net adjustments in the estimated fair value of the liability for earnout obligations in connection with revised assumptions due to changes in interest rates, volatility and other assumptions and projections of future performance for 58 and 45 acquisitions, respectively. The net adjustments in the three‑month period ended June 30, 2024, include changes made to the estimated fair value of the Willis Re acquisition earnout and reflect updated assumptions as of June 30, 2024. The aggregate amount of maximum earnout obligations related to acquisitions was $ 1,925.8 million as of June 30, 2024 , of which $ 1,236.7 million was recorded in the consolidated balance sheet as of June 30, 2024 , based on the estimated fair value of the expected future payments to be made, of which approximately $ 491.8 million can be settled in cash or stock at our option and $ 744.9 million must be settled in cash. The following is a summary of the estimated fair values of the net assets acquired at the date of each acquisition made in the six-month period ended June 30, 2024 (in millions): Twenty-one Other EIS TRA OPR Acquisitions Total Cash and cash equivalents $ 0.1 $ 4.1 $ 0.8 $ 9.9 $ 14.9 Fiduciary assets 1.0 2.6 — 34.1 37.7 Other current assets 3.5 0.5 2.7 11.3 18.0 Fixed assets — 0.4 — 0.7 1.1 Noncurrent assets 0.1 1.7 2.0 3.8 7.6 Goodwill 27.4 65.8 41.9 205.9 341.0 Expiration lists 35.9 57.4 22.1 185.5 300.9 Non-compete agreements 0.5 0.6 0.2 6.2 7.5 Trade names — — — 0.3 0.3 Total assets acquired 68.5 133.1 69.7 457.7 729.0 Fiduciary liabilities 1.0 2.6 — 34.1 37.7 Current liabilities 0.8 0.6 1.1 14.7 17.2 Noncurrent liabilities 0.1 1.7 2.2 16.1 20.1 Total liabilities assumed 1.9 4.9 3.3 64.9 75.0 Total net assets acquired $ 66.6 $ 128.2 $ 66.4 $ 392.8 $ 654.0 Among other things, these acquisitions allow us to expand into desirable geographic locations, further extend our presence in the retail and wholesale insurance and reinsurance brokerage markets and increase the volume of general services currently provided. The excess of the purchase price over the estimated fair value of the tangible net assets acquired at the acquisition date was allocated to goodwill, expiration lists, non-compete agreements and trade names in the amounts of $ 341.0 million, $ 300.9 million, $ 7.5 million and $ 0.3 million, respectively, within the brokerage segment. Provisional estimates of fair value are established at the time of each acquisition and are subsequently reviewed and finalized within the first year of operations subsequent to the acquisition date to determine the necessity for adjustments. During this period, we may use independent third-party valuation specialists to assist us in finalizing the fair value of assets acquired and liabilities assumed. Fair value adjustments, if any, are most common to the values established for amortizable intangible assets, including expiration lists, non‑compete agreements and trade names, as well as for acquired software, and earnout liabilities, with the offset to goodwill, net of any income tax effect. Provisional estimates of fair value were used by us to initially record four acquisitions as of their acquisition date that were completed in the fourth quarter of 2023. We subsequently used independent third party valuation specialists to assist us in determining the fair value of assets acquired and liabilities assumed for these transactions, the valuations of which were completed in the three-month period ended June 30, 2024. Based on these valuations, we made adjustments to the amounts initially recorded for earnout liabilities, expiration lists, non-competes agreements, trade names and acquired software, which resulted in a net increase to goodwill of $ 256.7 million. The fair value of the tangible assets and liabilities for each applicable acquisition at the acquisition date approximated their carrying values. In general, the fair value of expiration lists was established using the excess earnings method, which is an income approach based on estimated financial projections developed by management for each acquired entity using market participant assumptions. Revenue growth and attrition rates generally ranged from 0.7 % to 5.3 % and 5.0 % to 11.0 %, respectively, for our 2023 acquisitions for which valuations were performed in 2024. We estimate the fair value as the present value of the benefits anticipated from ownership of the subject expiration list in excess of returns required on the investment in contributory assets necessary to realize those benefits. The rate used to discount the net benefits was based on a risk-adjusted rate that takes into consideration market-based rates of return and reflects the risk of the asset relative to the acquired business. The discount rates ranged from 9.5 % to 11.0 % for our 2023 acquisitions for which valuations were performed in 2024. The fair value of non-compete agreements was established using the profit differential method, which is an income approach based on estimated financial projections developed by management for the acquired company using market participant assumptions and various non-compete scenarios. Expiration lists, non-compete agreements and trade names related to our acquisitions are amortized using the straight-line method over their estimated useful lives ( two to fifteen years for expiration lists, two to six years for non-compete agreements and two to fifteen years for trade names), while goodwill is not subject to amortization. We use the straight-line method to amortize these intangible assets because the pattern of their economic benefits cannot be reasonably determined with any certainty. We review all of our identifiable intangible assets for impairment periodically (at least annually) and whenever events or changes in business circumstances indicate that the carrying value of the assets may not be recoverable. In reviewing identifiable intangible assets, if the undiscounted future cash flows were less than the carrying amount of the respective (or underlying) asset, an indicator of impairment would exist and further analysis would be required to determine whether or not a loss would need to be charged against current period earnings as a component of amortization expense. Based on the results of impairment reviews during the three and six-month periods ended June 30, 2024 we wrote off $ 14.0 million of amortizable assets related to the brokerage segment. Based on the results of impairment reviews during the three and six-month periods ended June 30, 2023 , we wrote off $ 3.1 million and $ 3.2 million, respectively, of amortizable assets related to the brokerage and risk management segments. Of the $ 300.9 million of expiration lists, $ 7.5 million of non-compete agreements and $ 0.3 million of trade names related to our acquisitions made during the six-month period ended June 30, 2024 , $ 52.1 million, $ 4.1 million and $ 0.3 million, respectively, are not expected to be deductible for income tax purposes. Accordingly, we recorded a deferred tax liability of $ 13.1 million and a corresponding amount of goodwill in the six-month period ended June 30, 2024, related to the nondeductible amortizable intangible assets. Our unaudited consolidated financial statements for the six-month period ended June 30, 2024 include the operations of the entities acquired in the six-month period ended June 30, 2024 from their respective acquisition dates. The following is a summary of the unaudited pro forma historical results, as if these entities had been acquired at January 1, 2023 (in millions, except per share data) : Three-month period ended Six-month period ended June 30, June 30, 2024 2023 2024 2023 Total revenues $ 2,785.4 $ 2,478.5 $ 6,061.9 $ 5,223.0 Net earnings attributable to controlling interests 283.9 235.8 893.7 724.9 Basic net earnings per share 1.30 1.10 4.10 3.38 Diluted net earnings per share 1.27 1.07 4.02 3.32 The unaudited pro forma results above have been prepared for comparative purposes only and do not purport to be indicative of the results of operations which actually would have resulted had these acquisitions occurred at January 1, 2023, nor are they necessarily indicative of future operating results. Annualized revenues of entities acquired during the six-month period ended June 30, 2024 totaled approximately $ 141.2 million. For the six-month period ended June 30, 2024, total revenues, net pre-tax loss and net earnings before interest, income taxes, depreciation, amortization and the change in estimated acquisition earnout payables (EBITDAC) recorded in our unaudited consolidated statement of earnings related to our acquisitions made during the six-month period ended June 30, 2024 in the aggregate, were $ 42.8 million, $( 5.0 ) million and $ 7.4 million, respectively.

Contracts with Customers

Contracts with Customers	6 Months Ended
	Jun. 30, 2024
Revenue from Contract with Customer [Abstract]
Contracts with Customers	4. Contracts with Customers Contract Assets and Liabilities/Contract Balances Information about unbilled receivables, contract assets and contract liabilities from contracts with customers is as follows (in millions): June 30, December 31, Unbilled receivables $ 1,536.6 $ 1,093.7 Deferred contract costs 123.0 169.1 Deferred revenue 762.9 706.2 The unbilled receivables, which are included in accounts receivable in our consolidated balance sheet, primarily relate to our rights to consideration for work completed but not billed at the reporting date. These are transferred to the receivables when the client is billed. The deferred contract costs represent the costs we incur to fulfill a new or renewal contract with our clients prior to the effective date of the contract. These costs are expensed on the contract effective date. The deferred revenue in the consolidated balance sheet includes amounts that represent the remaining performance obligations under our contracts and amounts collected related to advanced billings and deposits received from customers that may or may not ultimately be recognized as revenues in the future. Deposits received from customers could be returned to the customers based on lesser actual transactional volume than originally billed volume. Significant changes in the deferred revenue balances, which include foreign currency translation adjustments, during the period are as follows (in millions): Risk Brokerage Management Total Deferred revenue at December 31, 2023 $ 533.6 $ 172.6 $ 706.2 Incremental deferred revenue 417.5 45.5 463.0 Revenue recognized during the six-month period ended ( 343.5 ) ( 42.1 ) ( 385.6 ) Net change in collected billings/deposits received from customers ( 22.8 ) ( 0.9 ) ( 23.7 ) Impact of change in foreign exchange rates ( 2.2 ) ( 0.1 ) ( 2.3 ) Deferred revenue recognized from business acquisitions 5.3 — 5.3 Deferred revenue at June 30, 2024 $ 587.9 $ 175.0 $ 762.9 Revenue recognized during the six-month period ended June 30, 2024 in the table above included revenue from 2023 acquisitions that would not be reflected in prior periods. Remaining Performance Obligations Remaining performance obligations represent the portion of the contract price for which work has not been performed. As of June 30, 2024, the aggregate amount of the contract price allocated to remaining performance obligations was $ 762.9 million. The estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied (or partially unsatisfied) at the end of the reporting period is as follows (in millions): Brokerage Risk Total 2024 (remaining six months) $ 504.9 $ 86.4 $ 591.3 2025 64.2 38.9 103.1 2026 16.8 17.4 34.2 2027 1.0 13.0 14.0 2028 0.5 6.8 7.3 Thereafter 0.5 12.5 13.0 Total $ 587.9 $ 175.0 $ 762.9 Deferred Contract Costs We capitalize costs incurred to fulfill contracts as deferred contract costs which are included in other current assets in our consolidated balance sheet. Deferred contract costs were $ 123.0 million and $ 169.1 million as of June 30, 2024 and December 31, 2023, respectively. Capitalized fulfillment costs are amortized to expense on the contract effective date. The amount of amortization of the deferred contract costs was $ 362.9 million and $ 306.7 million for the six-month periods ended June 30, 2024 and 2023, respectively. We have applied the practical expedient to recognize the incremental costs of obtaining contracts as an expense when incurred if the amortization period of the assets that we otherwise would have recognized is one year or less for our brokerage segment. These costs are included in compensation and operating expenses in our consolidated statement of earnings.

Intangible Assets

Intangible Assets	6 Months Ended
	Jun. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	5. Intangible Assets The carrying amount of goodwill at June 30, 2024 and December 31, 2023 allocated by domestic and foreign operations is as follows (in millions): Brokerage Risk Corporate Total At June 30, 2024 United States $ 6,651.7 $ 74.8 $ — $ 6,726.5 United Kingdom 2,503.1 18.4 — 2,521.5 Canada 606.8 — — 606.8 Australia 522.6 234.5 — 757.1 New Zealand 197.0 9.2 — 206.2 Other foreign 1,078.5 — 18.9 1,097.4 Total goodwill $ 11,559.7 $ 336.9 $ 18.9 $ 11,915.5 At December 31, 2023 United States $ 6,304.5 $ 74.8 $ — $ 6,379.3 United Kingdom 2,493.4 18.5 — 2,511.9 Canada 623.7 — — 623.7 Australia 514.6 135.9 — 650.5 New Zealand 204.2 9.6 — 213.8 Other foreign 1,077.4 — 19.0 1,096.4 Total goodwill $ 11,217.8 $ 238.8 $ 19.0 $ 11,475.6 The changes in the carrying amount of goodwill for the six-month period ended June 30, 2024 are as follows (in millions): Brokerage Risk Corporate Total Balance as of December 31, 2023 $ 11,217.8 $ 238.8 $ 19.0 $ 11,475.6 Goodwill acquired during the period 341.0 — — 341.0 Goodwill true-ups due to appraisals and other acquisition 94.4 102.0 — 196.4 Goodwill written-off related to sales of business and impairment ( 5.8 ) — — ( 5.8 ) Foreign currency translation adjustments during the period ( 87.7 ) ( 3.9 ) ( 0.1 ) ( 91.7 ) Balance as of June 30, 2024 $ 11,559.7 $ 336.9 $ 18.9 $ 11,915.5 Major classes of amortizable intangible assets at June 30, 2024 and December 31, 2023 consist of the following (in millions): June 30, December 31, 2024 2023 Expiration lists $ 8,341.8 $ 8,222.8 Accumulated amortization - expiration lists ( 4,025.8 ) ( 3,733.2 ) 4,316.0 4,489.6 Non-compete agreements 103.3 112.2 Accumulated amortization - non-compete agreements ( 79.9 ) ( 74.9 ) 23.4 37.3 Trade names 119.7 171.8 Accumulated amortization - trade names ( 69.7 ) ( 65.4 ) 50.0 106.4 Net amortizable assets $ 4,389.4 $ 4,633.3 Estimated aggregate amortization expense for each of the next five years and thereafter is as follows (in millions): 2024 (remaining six months) $ 310.1 2025 587.5 2026 544.3 2027 510.5 2028 470.1 Thereafter 1,966.9 Total $ 4,389.4

Credit and Other Debt Agreement

Credit and Other Debt Agreements	6 Months Ended
	Jun. 30, 2024
Debt Disclosure [Abstract]
Credit and Other Debt Agreements	6. Credit and Other Debt Agreements The following is a summary of our corporate and other debt (in millions): June 30, December 31, 2024 2023 Senior Notes: Semi-annual payments of interest, fixed rate of 2.40 %, balloon due November 9, 2031 $ 400.0 $ 400.0 Semi-annual payments of interest, fixed rate of 5.50 %, balloon due March 2, 2033 350.0 350.0 Semi-annual payments of interest, fixed rate of 6.50 %, balloon due February 15, 2034 400.0 400.0 Semi-annual payments of interest, fixed rate of 5.45 %, balloon due July 15, 2034 500.0 — Semi-annual payments of interest, fixed rate of 3.50 %, balloon due May 20, 2051 850.0 850.0 Semi-annual payments of interest, fixed rate of 3.05 %, balloon due March 9, 2052 350.0 350.0 Semi-annual payments of interest, fixed rate of 5.75 %, balloon due March 2, 2053 600.0 600.0 Semi-annual payments of interest, fixed rate of 6.75 %, balloon due February 15, 2054 600.0 600.0 Semi-annual payments of interest, fixed rate of 5.75 %, balloon due July 15, 2054 500.0 — Total Senior Notes 4,550.0 3,550.0 Note Purchase Agreements: Semi-annual payments of interest, fixed rate of 4.72 %, balloon due February 13, 2024 — 100.0 Semi-annual payments of interest, fixed rate of 4.58 %, balloon due February 27, 2024 — 325.0 Semi-annual payments of interest, fixed rate of 4.31 %, balloon due June 24, 2025 200.0 200.0 Semi-annual payments of interest, fixed rate of 4.85 %, balloon due February 13, 2026 140.0 140.0 Semi-annual payments of interest, fixed rate of 4.73 %, balloon due February 27, 2026 175.0 175.0 Semi-annual payments of interest, fixed rate of 4.40 %, balloon due June 2, 2026 175.0 175.0 Semi-annual payments of interest, fixed rate of 4.36 %, balloon due June 24, 2026 150.0 150.0 Semi-annual payments of interest, fixed rate of 3.75 %, balloon due January 30, 2027 30.0 30.0 Semi-annual payments of interest, fixed rate of 4.09 %, balloon due June 27, 2027 125.0 125.0 Semi-annual payments of interest, fixed rate of 4.09 %, balloon due August 2, 2027 125.0 125.0 Semi-annual payments of interest, fixed rate of 4.14 %, balloon due August 4, 2027 98.0 98.0 Semi-annual payments of interest, fixed rate of 3.46 %, balloon due December 1, 2027 100.0 100.0 Semi-annual payments of interest, fixed rate of 4.55 %, balloon due June 2, 2028 75.0 75.0 Semi-annual payments of interest, fixed rate of 4.34 %, balloon due June 13, 2028 125.0 125.0 Semi-annual payments of interest, fixed rate of 5.04 %, balloon due February 13, 2029 100.0 100.0 Semi-annual payments of interest, fixed rate of 4.98 %, balloon due February 27, 2029 100.0 100.0 Semi-annual payments of interest, fixed rate of 4.19 %, balloon due June 27, 2029 50.0 50.0 Semi-annual payments of interest, fixed rate of 4.19 %, balloon due August 2, 2029 50.0 50.0 Semi-annual payments of interest, fixed rate of 3.48 %, balloon due December 2, 2029 50.0 50.0 Semi-annual payments of interest, fixed rate of 3.99 %, balloon due January 30, 2030 341.0 341.0 Semi-annual payments of interest, fixed rate of 4.44 %, balloon due June 13, 2030 125.0 125.0 Semi-annual payments of interest, fixed rate of 5.14 %, balloon due March 13, 2031 180.0 180.0 Semi-annual payments of interest, fixed rate of 4.70 %, balloon due June 2, 2031 25.0 25.0 Semi-annual payments of interest, fixed rate of 4.09 %, balloon due January 30, 2032 69.0 69.0 Semi-annual payments of interest, fixed rate of 4.34 %, balloon due June 27, 2032 75.0 75.0 Semi-annual payments of interest, fixed rate of 4.34 %, balloon due August 2, 2032 75.0 75.0 Semi-annual payments of interest, fixed rate of 4.59 %, balloon due June 13, 2033 125.0 125.0 Semi-annual payments of interest, fixed rate of 5.29 %, balloon due March 13, 2034 40.0 40.0 Semi-annual payments of interest, fixed rate of 4.48 %, balloon due June 12, 2034 175.0 175.0 Semi-annual payments of interest, fixed rate of 4.24 %, balloon due January 30, 2035 79.0 79.0 Semi-annual payments of interest, fixed rate of 2.44 %, balloon due February 10, 2036 100.0 100.0 Semi-annual payments of interest, fixed rate of 2.46 %, balloon due May 5, 2036 75.0 75.0 Semi-annual payments of interest, fixed rate of 4.69 %, balloon due June 13, 2038 75.0 75.0 Semi-annual payments of interest, fixed rate of 5.45 %, balloon due March 13, 2039 40.0 40.0 Semi-annual payments of interest, fixed rate of 4.49 %, balloon due January 30, 2040 56.0 56.0 Total Note Purchase Agreements 3,523.0 3,948.0 Credit Agreement: Periodic payments of interest and principal, prime or SOFR plus up 1.075 %, expires June 22, 2028 80.0 245.0 Premium Financing Debt Facility - expires October 31, 2025 : Facility B AUD denominated tranche, interbank rates plus 1.500 % 199.6 249.0 NZD denominated tranche, interbank rates plus 1.850 % — — Facility C and D AUD denominated tranche, interbank rates plus 0.830 % — 31.4 NZD denominated tranche, interbank rates plus 0.990 % 8.2 8.6 Total Premium Financing Debt Facility 207.8 289.0 Total corporate and other debt 8,360.8 8,032.0 Less unamortized debt acquisition costs on Senior Notes and Note Purchase Agreements ( 46.8 ) ( 38.4 ) Less unamortized discount on Bonds Payable ( 35.3 ) ( 28.6 ) Net corporate and other debt $ 8,278.7 $ 7,965.0 Senior Notes - On February 12, 2024, we closed and funded an offering of $ 1,000.0 million of unsecured senior notes in two tranches. The $ 500.0 million aggregate principal amount of 5.45 % Senior Notes is due in 2034 (which we refer to as the 2034 July Notes) and $ 500.0 million aggregate principal amount of 5.75 % Senior Notes is due in 2054 (which we refer to as the 2054 July Notes). The weighted average interest rate is 5.71 % per annum after giving effect to underwriting costs and a net hedge loss. During 2023, we entered into a pre-issuance interest rate hedging transaction related to these notes. We realized a net cash loss of approximately $ 1.4 million on the hedging transactions that will be recognized on a pro rata basis as an increase to our reported interest expense over ten years . We used the proceeds of these offerings to fund acquisitions, earnout payments related to acquisitions and general corporate purposes.

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2024
Earnings Per Share [Abstract]
Earnings Per Share	7. Earnings Per Share The following table sets forth the computation of basic and diluted net earnings per share (in millions, except per share data): Three-month period ended Six-month period ended June 30, June 30, 2024 2023 2024 2023 Net earnings attributable to controlling interests $ 283.4 $ 234.5 $ 891.8 $ 721.0 Weighted average number of common shares outstanding 218.8 214.9 218.1 213.8 Dilutive effect of stock options using the treasury 4.1 4.1 4.3 4.2 Weighted average number of common and common 222.9 219.0 222.4 218.0 Basic net earnings per share $ 1.30 $ 1.09 $ 4.09 $ 3.37 Diluted net earnings per share $ 1.27 $ 1.07 $ 4.01 $ 3.31 Anti-dilutive stock-based awards of 1.0 million and 1.1 million shares were outstanding at the three-month periods ended June 30, 2024 and 2023 , respectively, which were excluded in the computation of the dilutive effect of stock-based awards for the three-month periods then ended. Anti-dilutive stock-based awards of 0.7 million shares were outstanding at each the six-month periods ended June 30, 2024 and 2023 , which were excluded in the computation of the dilutive effect of stock-based awards for the six-month periods then ended. These stock‑based awards were excluded from the computation because the exercise prices on these stock‑based awards were greater than the average market price of our common shares during the respective period, and therefore, would be anti‑dilutive to earnings per share under the treasury stock method.

Stock Option Plans

Stock Option Plans	6 Months Ended
	Jun. 30, 2024
Text Block [Abstract]
Stock Option Plans	8. Stock Option Plans On May 10, 2022, our stockholders approved the Arthur J. Gallagher & Co. 2022 Long-Term Incentive Plan (which we refer to as the LTIP), which replaced our previous stockholder-approved Arthur J. Gallagher & Co. 2017 Long-Term Incentive Plan (which we refer to as the 2017 LTIP). The LTIP term began May 10, 2022 and terminates on the date of the annual meeting of stockholders in 2032, unless terminated earlier by our board of directors. All of our officers, employees and non-employee directors are eligible to receive awards under the LTIP. The compensation committee of our board of directors determines the annual number of shares delivered under the LTIP. The LTIP provides for non-qualified and incentive stock options, stock appreciation rights, restricted stock and restricted stock units, any or all of which may be made contingent upon the achievement of performance criteria. Shares of our common stock available for issuance under the LTIP include authorized and unissued shares of common stock or authorized and issued shares of common stock reacquired and held as treasury shares or otherwise, or a combination thereof. The number of available shares will be reduced by the aggregate number of shares that become subject to outstanding awards granted under the LTIP. A maximum of 3.5 million shares issued for full value awards (i.e., awards other than stock options or stock appreciation rights) will be counted one-for-one against the 13.5 million share pool, and every share subject to a full value award in excess of such limit will count as 3.8 shares against the pool. To the extent that shares subject to an outstanding award granted under either the LTIP or prior equity plans are not issued or delivered by reason of the expiration, termination, cancellation or forfeiture of such award or by reason of the settlement of such award in cash, then such shares will again be available for grant under the LTIP. The maximum number of shares available under the LTIP for restricted stock, restricted stock unit awards and performance unit awards settled with stock (i.e., all awards other than stock options and stock appreciation rights) was 2.5 million at June 30, 2024. The LTIP provides for the grant of stock options, which may be either tax-qualified incentive stock options or non-qualified stock options and stock appreciation rights. The compensation committee determines the period for the exercise of a non-qualified stock option, tax-qualified incentive stock option or stock appreciation right, provided that no option can be exercised later than seven years after its date of grant. The exercise price of a non-qualified stock option or tax-qualified incentive stock option and the base price of a stock appreciation right cannot be less than 100 % of the fair market value of a share of our common stock on the date of grant, provided that the base price of a stock appreciation right granted in tandem with an option will be the exercise price of the related option. Upon exercise, the option exercise price may be paid in cash, by the delivery of previously owned shares of our common stock, through a net-exercise arrangement, or through a broker-assisted cashless exercise arrangement. The compensation committee determines all of the terms relating to the exercise, cancellation or other disposition of an option or stock appreciation right upon a termination of employment, whether by reason of disability, retirement, death or any other reason. Stock option and stock appreciation right awards under the LTIP are non-transferable. On March 1, 2024, the compensation committee granted 1,044,000 options under the LTIP to our officers and key employees that become exercisable at the rate of 34 %, 33 % and 33 % on the anniversary date of the grant in 2027, 2028 and 2029, respectively. On March 15, 2023, the compensation committee granted 1,131,000 options under the LTIP to our officers and key employees that become exercisable at the rate of 34 %, 33 % and 33 % on the anniversary date of the grant in 2026, 2027 and 2028, respectively. The 2024 and 2023 options expire seven years from the date of grant, or earlier in the event of certain terminations of employment. Stock options granted in 2023 to certain executive officers age 55 or older are not subject to forfeiture upon such officers' departure from the company after two years from date of grant. Stock options granted in 2024 to executive officers are not subject to forfeiture upon such officers’ departure from the company once they attain the age of 62 . During the three-month periods ended June 30, 2024 and 2023 , we recognized $ 10.5 million and $ 7.8 million, respectively, of compensation expense related to our stock option grants. During the six-month periods ended June 30, 2024 and 2023 , we recognized $ 25.6 million and $ 15.5 million, respectively, of compensation expense related to our stock option grants. For purposes of expense recognition, the estimated fair values of the stock option grants are amortized to expense over the options’ vesting period. We estimated the fair value of stock options at the date of grant using the Black-Scholes option pricing model with the following weighted average assumptions: 2024 2023 Expected dividend yield 1.0 % 1.2 % Expected risk-free interest rate 4.2 % 3.6 % Volatility 25.3 % 25.0 % Expected life (in years) 5.5 5.4 Option valuation models require the input of highly subjective assumptions including the expected stock price volatility. The Black-Scholes option pricing model was developed for use in estimating the fair value of traded options which have no vesting restrictions and are fully transferable. The weighted average fair value per option for all options granted during the six-month periods ended June 30, 2024 and 2023 , as determined on the grant date using the Black-Scholes option pricing model, was $ 69.55 and $ 46.48 , respectively. The following is a summary of our stock option activity and related information for 2024 (in millions, except exercise price and year data): Six-month period ended June 30, 2024 Weighted Average Weighted Remaining Shares Average Contractual Aggregate Under Exercise Term Intrinsic Option Price (in years) Value Beginning balance 7.9 $ 123.85 Granted 1.0 243.54 Exercised ( 1.0 ) 76.40 Forfeited or canceled ( 0.1 ) 151.05 Ending balance 7.8 $ 145.70 4.18 $ 883.9 Exercisable at end of period 2.1 $ 88.79 2.19 $ 353.9 Ending unvested and expected to vest 5.2 $ 164.50 4.86 $ 494.1 Options with respect to 10.9 million shares (less any shares of restricted stock issued under the LTIP - see Note 10 to these unaudited consolidated financial statements) were available for grant under the LTIP at June 30, 2024. The total intrinsic value of options exercised during the six-month periods ended June 30, 2024 and 2023 was $ 173.7 million and $ 123.8 million, respectively. As of June 30, 2024 , we had approximately $ 149.9 million of total unrecognized compensation expense related to nonvested options. We expect to recognize that cost over a weighted average period of approximately four years . Other information regarding stock options outstanding and exercisable at June 30, 2024 is summarized as follows (in millions, except exercise price and year data): Options Outstanding Options Exercisable Weighted Average Remaining Weighted Weighted Contractual Average Average Number Term Exercise Number Exercise Range of Exercise Prices Outstanding (in years) Price Exercisable Price $ 70.74 — $ 70.74 0.4 0.71 $ 70.74 0.4 $ 70.74 79.59 — 79.59 0.7 1.70 79.59 0.7 79.59 86.17 — 86.17 1.1 2.70 86.17 0.6 86.17 127.90 — 127.90 1.4 3.71 127.90 0.4 127.90 156.85 — 156.85 1.0 4.59 156.85 — — 158.56 — 161.14 1.1 4.72 158.65 — — 177.09 — 202.13 1.1 5.72 177.78 — — 238.88 — 243.54 1.0 6.67 243.54 — — $ 70.74 — $ 243.54 7.8 4.18 $ 145.70 2.1 $ 88.79

Deferred Compensation

Deferred Compensation	6 Months Ended
	Jun. 30, 2024
Compensation Related Costs [Abstract]
Deferred Compensation	9. Deferred Compensation We have a Deferred Equity Participation Plan (which we refer to as the DEPP), which is a non-qualified plan that generally provides for distributions to certain of our key executives when they reach age 62 (or the one-year anniversary of the date of the grant for participants over the age of 61 as of the grant date) or upon or after their actual retirement if later. Under the provisions of the DEPP, we typically contribute cash in an amount approved by the compensation committee to a rabbi trust on behalf of the executives participating in the DEPP, and instruct the trustee to acquire a specified number of shares of our common stock on the open market or in privately negotiated transactions based on participant elections. Distributions under the DEPP may not normally be made until the participant reaches age 62 (or the one-year anniversary of the date of the grant for participants over the age of 61 as of the grant date) and are subject to forfeiture in the event of voluntary termination of employment or termination for cause prior to then. DEPP awards are generally made annually in the first quarter. In addition, we annually make awards under sub-plans of the DEPP for certain production staff, which generally provide for vesting and/or distributions no sooner than five years from the date of awards, although certain awards vest and/or distribute after the earlier of fifteen years or the participant reaching age 65 . All contributions to the plan (including sub-plans) deemed to be invested in shares of our common stock are distributed in the form of our common stock and all other distributions are paid in cash. Our common stock that is issued to or purchased by the rabbi trust as a contribution under the DEPP is valued at historical cost, which equals its fair market value at the date of grant or date of purchase. When common stock is issued, we record an unearned deferred compensation obligation as a reduction of capital in excess of par value in the accompanying consolidated balance sheet, which is amortized to compensation expense ratably over the vesting period of the participants. Future changes in the fair market value of our common stock owed to the participants do not have any impact on the amounts recorded in our unaudited consolidated financial statements. In the first quarters of 2024 and 2023, the compensation committee approved $ 23.2 million and $ 25.1 million, respectively, of awards in the aggregate to certain key executives under the DEPP that were contributed to the rabbi trust in the first quarters of 2024 and 2023, respectively. We contributed cash to the rabbi trust and instructed the trustee to acquire a specified number of shares of our common stock on the open market to fund these 2024 and 2023 awards. During the three-month periods ended June 30, 2024 and 2023 , we charged $ 5.6 million and $ 5.9 million, respectively, to compensation expense related to these awards. During the six-month periods ended June 30, 2024 and 2023 , we charged $ 9.6 million and $ 9.9 million, respectively, to compensation expense related to these awards. In the first quarters of 2024 and 2023, the compensation committee approved $ 2.3 million and $ 3.0 million, respectively, of awards under the sub-plans referred to above, which were contributed to the rabbi trust in the first quarters of 2024 and 2023, respectively. During the three-month periods ended June 30, 2024 and 2023 , we charged $ 0.6 million and $ 0.8 million, respectively, to compensation expense related to these awards. During the six-month periods ended June 30, 2024 and 2023 , we charged $ 1.1 million and $ 1.4 million, respectively, to compensation expense related to these awards. There were $ 2.3 million of distributions from the sub-plans during the six-month period ended June 30, 2024 . There were $ 6.4 million of distributions from the sub‑plans during the six-month period ended June 30, 2023. At June 30, 2024 and December 31, 2023, we recorded $ 95.5 million (related to 2.3 million shares) and $ 81.1 million (related to 2.2 million shares), respectively, of unearned deferred compensation as a reduction of capital in excess of par value in the accompanying consolidated balance sheet. The total intrinsic value of our unvested equity-based awards under the plan at June 30, 2024 and December 31, 2023 was $ 584.4 million and $ 504.9 million, respectively. During the six-month periods ended June 30, 2024 and 2023 , cash and equity awards with an aggregate fair value of $ 17.9 million and $ 9.4 million, respectively, were vested and distributed to executives under the DEPP. We have a Deferred Cash Participation Plan (which we refer to as the DCPP), which is a non-qualified deferred compensation plan for certain key employees, other than executive officers, that generally provides for vesting and/or distributions no sooner than five years from the date of awards. Under the provisions of the DCPP, we typically contribute cash in an amount approved by the compensation committee to the rabbi trust on behalf of the executives participating in the DCPP, and instruct the trustee to acquire a specified number of shares of our common stock on the open market or in privately negotiated transactions based on participant elections. In the first quarters of 2024 and 2023, the compensation committee approved $ 8.1 million and $ 9.8 million, respectively, of awards in the aggregate to certain key executives under the DCPP that were contributed to the rabbi trust in the first quarters of 2024 and 2023, respectively. During the three-month periods ended June 30, 2024 and 2023 , we charged $ 5.1 million and $ 4.2 million, respectively, to compensation expense related to these awards. During the six-month periods ended June 30, 2024 and 2023 , we charged $ 9.9 million and $ 8.0 million, respectively, to compensation expense related to these awards. There were $ 13.6 million of distributions from the DCPP during the six-month period ended June 30, 2024 . There were $ 19.5 million of distributions from the DCPP during the six-month period ended June 30, 2023 .

Restricted Stock, Performance S

Restricted Stock, Performance Share and Cash Awards	6 Months Ended
	Jun. 30, 2024
Text Block [Abstract]
Restricted Stock, Performance Share and Cash Awards	10. Restricted Stock, Performance Share and Cash Awards Restricted Stock Awards As discussed in Note 8 to these unaudited consolidated financial statements, on May 10, 2022, our stockholders approved the LTIP, which replaced our previous stockholder-approved 2017 LTIP. The LTIP provides for the grant of a stock award either as restricted stock or as restricted stock units to officers, employees and non-employee directors. In either case, the compensation committee may determine that the award will be subject to the attainment of performance measures over an established performance period. Stock awards and the related dividend equivalents are non-transferable and subject to forfeiture if the holder does not remain continuously employed with us during the applicable restriction period or, in the case of a performance-based award, if applicable performance measures are not attained. The compensation committee will determine all of the terms relating to the satisfaction of performance measures and the termination of a restriction period, or the forfeiture and cancellation of a restricted stock award upon a termination of employment, whether by reason of disability, retirement, death or any other reason. The agreements awarding restricted stock units under the LTIP will specify whether such awards may be settled in shares of our common stock, cash or a combination of shares and cash and whether the holder will be entitled to receive dividend equivalents, on a current or deferred basis, with respect to such award. Prior to the settlement of a restricted stock unit, the holder of a restricted stock unit will have no rights as a stockholder of the company. The maximum number of shares available under the LTIP for restricted stock, restricted stock units and performance unit awards settled with stock (i.e., all awards other than stock options and stock appreciation rights) is 4.0 million. At June 30, 2024 , 2.5 million shares were available for grant under the LTIP for such awards. In the first quarters of 2024 and 2023, we granted 345,000 and 378,000 restricted stock units, respectively, to employees under the LTIP, with an aggregate fair value of $ 83.9 million and $ 67.0 million, respectively, at the date of grant. These 2024 and 2023 awards of restricted stock units vest in full based on continued employment through March 1, 2029 and March 15, 2028 , respectively. We account for restricted stock awards at historical cost, which equals its fair market value at the date of grant, which is amortized to compensation expense ratably over the vesting period of the participants. Future changes in the fair market value of our common stock that is owed to the participants do not have any impact on the amounts recorded in our unaudited consolidated financial statements. During the three-month periods ended June 30, 2024 and 2023 , we recognized $ 14.1 million and $ 11.0 million, respectively, to compensation expense related to restricted stock unit awards granted in 2017 through 2023. During the six-month periods ended June 30, 2024 and 2023 , we recognized $ 27.0 million and $ 20.7 million, respectively, to compensation expense related to restricted stock unit awards granted in 2017 through 2023. The total intrinsic value of unvested restricted stock units at June 30, 2024 and 2023 was $ 512.7 million and $ 460.5 million, respectively. During the six-month periods ended June 30, 2024 and 2023 , equity awards (including accrued dividends) with an aggregate value of $ 93.3 million and $ 62.0 million, respectively, were vested and distributed to employees under this plan. Performance Share Awards On March 1, 2024 and March 15, 2023, pursuant to the LTIP, respectively, the compensation committee approved 58,000 and 58,000 , respectively, of provisional performance share awards, with an aggregate fair value of $ 14.2 million and $ 10.3 million, respectively, for future grants to our officers. Each performance share award was equivalent to the value of one share of our common stock on the date such provisional award was approved. At the end of the performance period, eligible participants will receive a number of earned shares based on the growth in adjusted EBITDAC per share (as defined in our 2024 Proxy Statement). Earned shares for the 2024 and 2023 provisional awards will fully vest based on continuous employment through March 1, 2027 and March 15, 2026, respectively, and will be settled in unrestricted shares of our common stock on a one-for-one basis as soon as practicable thereafter. The 2024 and 2023 awards are subject to a three-year performance period that began on January 1, 2024 and 2023, respectively, and vest on the three-year anniversary of the date of grant (March 1, 2027 and March 15, 2026). Performance share awards granted in 2023 to certain executive officers age 55 or older are not subject to forfeitures upon such officers' departure from the company after two years from date of grant. Performance share awards granted in 2024 to executive officers are not subject to forfeiture upon such officers’ departure from the company once they attain the age of 62 . In each case, the awards vest on a pro rata basis based on the number of months rounded up during which the officer was employed during the three-year performance period. During the three-month periods ended June 30, 2024 and 2023 , we recognized $ 5.6 million and $ 3.8 million, respectively, to compensation expense related to performance share awards granted in 2020 through 2024. During the six-month periods ended June 30, 2024 and 2023 , we recognized $ 10.6 million and $ 8.5 million, respectively, to compensation expense related to performance share awards granted in 2020 through 2024. The total intrinsic value of unvested performance share awards at June 30, 2024 and 2023 was $ 85.2 million and $ 64.3 million, respectively. During the six-month periods ended June 30, 2024 and 2023 , equity awards (including accrued dividends) with an aggregate fair value of $ 31.6 million and $ 28.9 million, respectively, were vested and distributed to employees under this plan. Cash Awards Pursuant to our Performance Unit Program (which we refer to as the Program), there were no units granted in the six-month periods ended June 30, 2024 and 2023 . The Program consists of a one-year performance period based on our financial performance and a three-year vesting period measured from January 1 of the year of grant. At the discretion of the compensation committee and determined based on our performance, the eligible officer or key employee will be granted a percentage of the provisional cash award units that equates to the EBITDAC growth achieved (as defined in the Program). At the end of the performance period, eligible participants will be granted a number of units based on achievement of the performance goal and subject to approval by the compensation committee. Granted units will fully vest based on continuous employment through the three-year vesting period. The ultimate award value will be equal to the trailing twelve-month price of our common stock, multiplied by the number of units subject to the award, but limited to between 0.5 and 1.5 times the original value of the units determined as of the grant date. The fair value of the awarded units will be paid out in cash as soon as practicable. If an eligible employee leaves us prior to the vesting date, the entire award will be forfeited. On March 15, 2022, pursuant to the Program, the compensation committee approved provisional cash awards of $ 19.9 million in the aggregate for future grants to our officers and key employees that are denominated in units ( 125,000 units in the aggregate), each of which was equivalent to the value of one share of our common stock on the date the provisional award was approved. During the three-month periods ended June 30, 2024 and 2023 , we recognized $ 3.3 million and $ 3.1 million, respectively, to compensation expense related to these awards. During the six-month periods ended June 30, 2024 and 2023 , we recognized $ 6.7 million and $ 5.7 million, respectively, to compensation expense related to these awards. On March 16, 2021, pursuant to the Program, the compensation committee approved provisional cash awards of $ 18.8 million in the aggregate for future grants to our officers and key employees that are denominated in units ( 147,000 units in the aggregate), each of which was equivalent to the value of one share of our common stock on the date the provisional award was approved. Based on our performance for 2021, we granted 143,000 units under the Program in the first quarter of 2022 that fully vested on January 1, 2024 . During the three and six-month periods ended June 30, 2023 , we recognized $ 3.2 million and $ 6.5 million, respectively, to compensation expense related to these awards. During the six-month period ended June 30, 2024 , cash awards related to the 2021 provisional award with an aggregate fair value of $ 25.4 million ( 129,000 units in the aggregate) were vested and distributed to employees under the program. During the six-month period ended June 30, 2023 , cash awards related to the 2020 provisional award with an aggregate fair value of $ 24.7 million ( 191,000 units in the aggregate) were vested and distributed to employees under the Program.

Derivatives and Hedging Activit

Derivatives and Hedging Activity	6 Months Ended
	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging Activity	11. Derivatives and Hedging Activity We are exposed to market risks, including changes in foreign currency exchange rates and interest rates. To manage the risk related to these exposures, we enter into various derivative instruments that reduce these risks by creating offsetting exposures. We generally do not enter into derivative transactions for trading or speculative purposes. Foreign Exchange Risk Management We are exposed to foreign exchange risk when we earn revenues, pay expenses, or enter into monetary intercompany transfers denominated in a currency that differs from our functional currency, or other transactions that are denominated in a currency other than our functional currency. We use foreign exchange derivatives, typically forward contracts and options, to reduce our overall exposure to the effects of currency fluctuations on cash flows. These exposures are hedged, on average, for less than three years. Interest Rate Risk Management We enter into various long-term debt agreements. We use interest rate derivatives, typically swaps, to reduce our exposure to the effects of interest rate fluctuations on the forecasted interest rates for up to three years into the future. We have not received or pledged any collateral related to derivative arrangements at June 30, 2024. The notional and fair values of derivatives designated as hedging instruments are as follows at June 30, 2024 and December 31, 2023 (in millions): Derivative Assets Derivative Liabilities Notional Balance Sheet Fair Balance Sheet Fair Instrument Amount Classification Value Classification Value At June 30, 2024 Interest rate contracts $ — Other current assets $ — Accrued compensation and other current liabilities $ — Other noncurrent assets — Other noncurrent liabilities — Foreign exchange contracts (1) 46.4 Other current assets 4.9 Accrued compensation and other current liabilities 2.6 Other noncurrent assets 10.1 Other noncurrent liabilities 4.1 Total $ 46.4 $ 15.0 $ 6.7 At December 31, 2023 Interest rate contracts $ 150.0 Other current assets $ — Accrued compensation and other current liabilities $ 5.7 Other noncurrent assets — Other noncurrent liabilities — Foreign exchange contracts (1) 67.8 Other current assets 3.9 Accrued compensation and other current liabilities 3.9 Other noncurrent assets 14.2 Other noncurrent liabilities 4.0 Total $ 217.8 $ 18.1 $ 13.6 (1) Included within foreign exchange contracts at June 30, 2024 were $ 819.3 million of call options, offset with $ 819.3 million of put options, and $ 3.0 million of buy forwards, offset with $ 49.4 million of sell forwards. Included within foreign exchange contracts at December 31, 2023 were $ 331.3 million of call options, offset with $ 331.3 million of put options, and $ 5.5 million of buy forwards, offset with $ 73.3 million of sell forwards. The effect of cash flow hedge accounting on accumulated other comprehensive loss for the six-month periods ended June 30, 2024 and 2023 was as follows (in millions): Amount of Amount of Gain Gain (Loss) Recognized Amount of Reclassified in Earnings Gain (Loss) from Related to Recognized in Accumulated Amount Accumulated Other Excluded Other Comprehensive from Comprehensive Loss into Effectiveness Statement of Earnings Instrument Loss (1) Earnings Testing Classification Three-month period ended June 30, 2024 Interest rate contracts $ ( 3.6 ) $ ( 0.3 ) $ — Interest expense Foreign exchange contracts ( 0.4 ) ( 1.0 ) — Commission revenue ( 0.4 ) 0.2 Compensation expense ( 0.4 ) 0.2 Operating expense Total $ ( 4.0 ) $ ( 2.1 ) $ 0.4 Three-month period ended June 30, 2023 Interest rate contracts $ 18.9 $ ( 0.3 ) $ — Interest expense Foreign exchange contracts 12.8 0.2 — Commission revenue ( 0.5 ) 0.4 Compensation expense ( 0.4 ) 0.3 Operating expense Total $ 31.7 $ ( 1.0 ) $ 0.7 Six-month period ended June 30, 2024 Interest rate contracts $ ( 2.9 ) $ ( 0.6 ) $ — Interest expense Foreign exchange contracts ( 3.8 ) ( 0.8 ) — Commission revenue ( 0.9 ) 0.5 Compensation expense ( 0.7 ) 0.4 Operating expense Total $ ( 6.7 ) $ ( 3.0 ) $ 0.9 Six-month period ended June 30, 2023 Interest rate contracts $ 8.8 $ ( 0.6 ) $ — Interest expense Foreign exchange contracts 28.7 0.8 — Commission revenue ( 1.0 ) 1.0 Compensation expense ( 0.7 ) 0.7 Operating expense Total $ 37.5 $ ( 1.5 ) $ 1.7 (1) For the three and six-month periods ended June 30, 2024 , the amount excluded from the assessment of hedge effectiveness for our foreign exchange contracts recognized in accumulated other comprehensive loss was a loss of $ 0.1 million and a gain of $ 0.2 million, respectively. For the three and six-month periods ended June 30, 2023 , the amount excluded from the assessment of hedge effectiveness for our foreign exchange contracts recognized in accumulated other comprehensive loss was a gain of $ 0.3 million and $ 0.8 million, respectively. We estimate that approximately $ 13.0 million of pretax gain currently included within accumulated other comprehensive loss will be reclassified into earnings in the next twelve months.

Commitments, Contingencies and

Commitments, Contingencies and Off-Balance Sheet Arrangements	6 Months Ended
	Jun. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments, Contingencies and Off-Balance Sheet Arrangements	12. Commitments, Contingencies and Off-Balance Sheet Arrangements In connection with our investing and operating activities, we have entered into certain contractual obligations and commitments. Our future minimum cash payments, including interest, associated with our contractual obligations pursuant to the Senior Notes, Note Purchase Agreements, Credit Agreement, Premium Financing Debt Facility, operating leases and purchase obligations at June 30, 2024 were as follows (in millions): Payments Due by Period Contractual Obligations 2024 2025 2026 2027 2028 Thereafter Total Senior Notes $ — $ — $ — $ — $ — $ 4,550.0 $ 4,550.0 Note Purchase Agreements — 200.0 640.0 478.0 200.0 2,005.0 3,523.0 Credit Agreement 80.0 — — — — — 80.0 Premium Financing Debt Facility 207.8 — — — — — 207.8 Interest on debt 184.4 374.0 355.0 336.7 317.2 4,285.8 5,853.1 Total debt obligations 472.2 574.0 995.0 814.7 517.2 10,840.8 14,213.9 Operating lease obligations 54.2 108.9 90.5 73.3 55.8 92.4 475.1 Less sublease arrangements ( 1.2 ) ( 1.8 ) ( 1.7 ) ( 1.6 ) ( 1.1 ) ( 0.8 ) ( 8.2 ) Outstanding purchase obligations 80.0 71.6 29.0 23.3 16.9 48.3 269.1 Total contractual obligations $ 605.2 $ 752.7 $ 1,112.8 $ 909.7 $ 588.8 $ 10,980.7 $ 14,949.9 The amounts presented in the table above may not necessarily reflect our actual future cash funding requirements, because the actual timing of the future payments made may vary from the stated contractual obligation. Senior Notes, Note Purchase Agreements, Credit Agreement and Premium Financing Debt Facility - See Note 6 to these unaudited consolidated financial statements for a summary of the amounts outstanding under the Senior Notes, Note Purchase Agreements, the Credit Agreement and Premium Financing Debt Facility. Operating Lease Obligations - Our corporate segment’s executive offices and certain subsidiary and branch facilities of our brokerage and risk management segments are located in a building we own at 2850 Golf Road, Rolling Meadows, Illinois, where we have approximately 360,000 square feet of space. We generally operate in leased premises at our other locations. Certain of these leases have options permitting renewals for additional periods. In addition to minimum fixed rentals, a number of leases contain annual escalation clauses which are generally related to increases in an inflation index. We have leased certain office space to several non-affiliated tenants under operating sublease arrangements. In the normal course of business, we expect that certain of these leases will not be renewed or replaced. We adjust charges for real estate taxes and common area maintenance annually based on actual expenses, and we recognize the related revenues in the year in which the expenses are incurred. These amounts are not included in the minimum future rentals to be received in the contractual obligations table above. Outstanding Purchase Obligations - The amount disclosed in the contractual obligations table above represents the aggregate amount of unrecorded purchase obligations that we had outstanding at June 30, 2024. These obligations represent agreements to purchase goods or services that were executed in the normal course of business. Off-Balance Sheet Commitments - Our total unrecorded commitments associated with outstanding letters of credit, and financial guarantees as of June 30, 2024 were as follows (in millions): Total Amount of Commitment Expiration by Period Amounts Off-Balance Sheet Commitments 2024 2025 2026 2027 2028 Thereafter Committed Letters of credit $ — $ — $ — $ — $ — $ 23.7 $ 23.7 Financial guarantees 1.0 — — — — — 1.0 Total commitments $ 1.0 $ — $ — $ — $ — $ 23.7 $ 24.7 Since commitments may expire unused, the amounts presented in the table above do not necessarily reflect our actual future cash funding requirements. See the Off‑Balance Sheet Debt section below for a discussion of our letters of credit. All of the letters of credit represent multiple year commitments that have annual, automatic renewing provisions and are classified by the latest commitment date. Since January 1, 2002, we have acquired 725 companies, all of which were accounted for using the acquisition method for recording business combinations. Substantially all of the purchase agreements related to these acquisitions contain provisions for potential earnout obligations. For all of our acquisitions made in the period from 2020 to 2024 that contain potential earnout obligations, such obligations are measured at fair value as of the acquisition date and are included on that basis in the recorded purchase price consideration for the respective acquisition. The amounts recorded as earnout payables are primarily based upon estimated future potential operating results of the acquired entities over a two- to three-year period subsequent to the acquisition date. The aggregate amount of the maximum earnout obligations related to these acquisitions was $ 1,925.8 million, of which $ 1,236.7 million was recorded in our consolidated balance sheet as of June 30, 2024 based on the estimated fair value of the expected future payments to be made, of which approximately $ 491.8 million can be settled in cash or stock at our option and $ 744.9 million must be settled in cash. Off-Balance Sheet Debt - Our unconsolidated investment portfolio includes investments in enterprises where our ownership interest is between 1 % and 50 %, in which management has determined that our level of influence and economic interest is not sufficient to require consolidation. As a result, these investments are accounted for under the equity method. None of these unconsolidated investments had any outstanding debt at June 30, 2024 or December 31, 2023, that was recourse to us. At June 30, 2024 , we had posted two letters of credit totaling $ 9.3 million, in the aggregate, related to our self‑insurance deductibles, for which we had a recorded liability of $ 14.0 million. We have an equity investment in a rent-a-captive facility, which we use as a placement facility for certain of our insurance brokerage operations. At June 30, 2024 , we had posted eight letters of credit totaling $ 13.0 million to allow certain of our captive operations to meet minimum statutory surplus requirements plus additional collateral related to premium and claim funds held in a fiduciary capacity, one letter of credit totaling $ 0.9 million for collateral related to claim funds held in a fiduciary capacity by a recent acquisition and one letter of credit totaling $ 0.5 million as a security deposit for a 2015 acquisition’s lease. These letters of credit have never been drawn upon. Litigation, Regulatory and Taxation Matters - We routinely are involved in legal proceedings, claims, disputes, regulatory matters and governmental inspections or investigations arising in the ordinary course of or incidental to our business, including those noted below in this section. We record accruals in the unaudited consolidated financial statements for pending litigation when we determine that an unfavorable outcome is probable and the amount of the loss can be reasonably estimated. For the matters we disclose that do not include an estimate of the amount of loss or range of losses, such an estimate is not possible or is immaterial, and we may be unable to estimate the possible loss or range of losses that could potentially result from the application of non-monetary remedies, unless disclosed below. We currently believe that the ultimate outcome of these proceedings, individually and in the aggregate, will not materially harm our financial position, results of operations or cash flows. However, legal proceedings and government investigations are subject to inherent uncertainties, and unfavorable rulings or other adverse events could occur, including the payment of substantial monetary damages or an injunction or other order prohibiting us from selling one or more products at all or in particular ways, precluding particular business practices or requiring other remedies, which may result in a material adverse impact on our business, results of operations or financial position. As previously disclosed, our IRC 831(b) (or “micro-captive”) advisory services business has been under audit by the IRS since 2013. Among other matters, the IRS is investigating whether we have been acting as a tax shelter promoter in connection with these operations. Additionally, the IRS is conducting a criminal investigation related to IRC 831(b) micro-captive underwriting enterprises. We have been advised that we are not a target of the criminal investigation. We are fully cooperating with both matters. Contingent Liabilities - We purchase insurance to provide protection from errors and omissions (which we refer to as E&O) claims that may arise during the ordinary course of business. Currently we retain the first $ 15.0 million of each and every E&O claim. In addition, we retain, in aggregate, up to another $ 2.0 million between $ 15.0 million and $ 100.0 million, plus up to another $ 10.0 million between $ 100.0 million and $ 225.0 million, and up to another $ 20.0 million between $ 225.0 million and $ 400.0 million. We have historically maintained self-insurance reserves for the portion of our E&O exposure that is not insured. We periodically determine a range of possible reserve levels using actuarial techniques that rely heavily on projecting historical claim data into the future. Our E&O reserve in the June 30, 2024 consolidated balance sheet is above the lower end of the most recently determined actuarial range by $ 6.2 million and below the upper end of the actuarial range by $ 8.8 million. We can make no assurances that the historical claim data used to project the current reserve levels will be indicative of future claim activity. Thus, the E&O reserve level and corresponding actuarial range could change in the future as more information becomes known, which could materially impact the amounts reported and disclosed herein. Tax-advantaged Investments No Longer Held - Between 1996 and 2007, we developed and then sold portions of our ownership in various energy related investments, many of which qualified for tax credits under IRC Section 29. We recorded tax benefits in connection with our ownership in these investments. At June 30, 2024 , we had exposure on $ 108.0 million of previously earned tax credits. Under the Tax Cuts and Jobs Act, a portion of these previously earned tax credits were refunded in 2019 for tax year 2018, according to a specific formula. Under the Coronavirus Aid, Relief, and Economic Security Act (the CARES Act), which was passed on March 27, 2020, we accelerated the refund of all remaining credits on April 17, 2020, and the remaining credits were refunded to us in the second quarter of 2020. In 2004, 2007 and 2009, the IRS examined several of these investments and all examinations were closed without any changes being proposed by the IRS. However, any future adverse tax audits, administrative rulings or judicial decisions could disallow previously claimed tax credits. Due to the contingent nature of this exposure and our related assessment of its likelihood, no reserve has been recorded in our June 30, 2024 consolidated balance sheet related to this exposure.

Supplemental Disclosures of Cas

Supplemental Disclosures of Cash Flow Information	6 Months Ended
	Jun. 30, 2024
Cash and Cash Equivalents [Abstract]
Supplemental Disclosures of Cash Flow Information	13. Supplemental Disclosures of Cash Flow Information Six-month period ended June 30, Supplemental disclosures of cash flow information (in millions): 2024 2023 Interest paid $ 162.1 $ 127.3 Income taxes paid, net 167.8 116.7 The following is a reconciliation of our end of period cash, cash equivalents, restricted cash and fiduciary cash balances as presented in the consolidated statement of cash flows for the six-month periods ended June 30, 2024 and 2023 (in millions): June 30, 2024 2023 Cash and cash equivalents - non-restricted cash $ 1,219.2 $ 777.9 Cash and cash equivalents - restricted cash 196.1 174.4 Total cash and cash equivalents 1,415.3 952.3 Fiduciary cash 5,422.5 5,989.9 Total cash, cash equivalents, restricted cash and fiduciary cash $ 6,837.8 $ 6,942.2 Fiduciary cash is included in fiduciary assets in our consolidated balance sheet. We have a qualified contributory savings and thrift 401(k) plan covering the majority of our domestic employees. For eligible employees who have met the plan’s age and service requirements to receive matching contributions, we historically have matched 100 % of pre-tax and Roth elective deferrals up to a maximum of 5.0 % of eligible compensation, subject to federal limits on plan contributions and not in excess of the maximum amount deductible for federal income tax purposes. Beginning in 2021, the amount matched by the company will be discretionary and annually determined by management. Employees must be employed and eligible for the plan on the last day of the plan year to receive a matching contribution, subject to certain exceptions enumerated in the plan document. Matching contributions are subject to a five-year graduated vesting schedule and can be funded in cash or company stock. We expensed (net of plan forfeitures) $ 56.0 million and $ 42.3 million related to the plan in the six-month periods ended June 30, 2024 and 2023 , respectively. During 2023, our board of directors authorized the 5.0 % employer matching contribution on eligible compensation to the 401(k) plan for the 2023 plan year to be funded with our common stock, which was funded in February 2024. During 2022, our board of directors authorized the 5.0 % employer matching contribution on eligible compensation to the 401(k) plan for the 2022 plan year to be funded with our common stock, which was funded in February 2023.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	6 Months Ended
	Jun. 30, 2024
Equity [Abstract]
Accumulated Other Comprehensive Loss	14. Accumulated Other Comprehensive Loss The after-tax components of our accumulated other comprehensive loss attributable to controlling interests consist of the following (in millions): Foreign Fair Value of Accumulated Pension Currency Derivative Comprehensive Liability Translation Investments Loss Balance as of December 31, 2023 $ ( 37.1 ) $ ( 867.4 ) $ 112.4 $ ( 792.1 ) Net change in period 0.2 ( 144.5 ) ( 2.8 ) ( 147.1 ) Balance as of June 30, 2024 $ ( 36.9 ) $ ( 1,011.9 ) $ 109.6 $ ( 939.2 ) The foreign currency translation during the six-month period ended June 30, 2024 relates to the net impact of changes in the value of the local currencies relative to the U.S. dollar for our operations in the Australia, Canada, the Caribbean, India, New Zealand, the U.K. and other non-U.S. locations. The reporting currency for our financial statements is the U.S. dollar. Certain of our assets, liabilities, expenses and revenues are denominated in currencies other than the U.S. dollar, primarily the Australian dollar, British pound, Canadian dollar and New Zealand dollar. To prepare our unaudited consolidated financial statements, we must translate those assets, liabilities, expenses and revenues into U.S. dollars at the applicable exchange rates. Assets and liabilities of non-U.S. dollar functional currency operations are translated into U.S. dollars at end-of-period exchange rates while revenues, expenses and cash flows are translated at average monthly exchange rates over the period. Equity is translated at historical exchange rates and the resulting cumulative translation adjustments are included as a component of accumulated other comprehensive loss in the consolidated balance sheet. The net change in the foreign currency translation during the six-month period ended June 30, 2024 primarily relates to goodwill (see Note 5 for the impact on goodwill) and amortizable intangible assets held by operations with a non-U.S. dollar functional currency. During the six-month periods ended June 30, 2024 and 2023 , $ 1.0 million and $ 2.6 million, of expense, respectively, related to the pension liability was reclassified from accumulated other comprehensive loss to compensation expense in the statement of earnings. During the six-month periods ended June 30, 2024 and 2023 , $ 3.0 million and $ 1.5 million of expense, respectively, related to the fair value of derivative investments, was reclassified from accumulated other comprehensive loss to the statement of earnings. During the six-month periods ended June 30, 2024 and 2023 , no amounts related to foreign currency translation were reclassified from accumulated other comprehensive loss to the statement of earnings.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2024
Segment Reporting [Abstract]
Segment Information	15. Segment Information We have three reportable segments: brokerage, risk management and corporate. The brokerage segment is primarily comprised of our retail and wholesale insurance and reinsurance brokerage operations. The brokerage segment (which comprises our retail property/casualty, wholesale, reinsurance, benefits and captive operations) generates revenues through commissions paid by underwriting enterprises and through fees charged to our clients. Our brokers, agents and administrators act as intermediaries between underwriting enterprises and our clients and we do not assume net underwriting risks. The risk management segment provides contract claim settlement and administration services for commercial, nonprofit, captive and public sector entities, and various organizations that choose to self-insure some or all of their property/casualty coverages and for underwriting enterprises that choose to outsource some or all of their property/casualty claims departments. These operations also provide claims management, loss control consulting and insurance property appraisal services. Revenues are principally generated on a negotiated per-claim or per-service fee basis. Our risk management segment also provides risk management consulting services that are recognized as the services are delivered. The corporate segment manages our clean energy and other investments. In addition, the corporate segment reports the financial information related to our debt and other corporate costs, external acquisition-related expenses and the impact of foreign currency remeasurements. Allocations of interest income and certain expenses are based on reasonable assumptions and estimates primarily using revenue, headcount and other information. We allocate the provision for income taxes to the brokerage and risk management segments using the local country statutory rates. Reported operating results by segment would change if different methods were applied. Financial information relating to our segments for the three and six-month periods ended June 30, 2024 and 2023 as follows (in millions): Three-month period ended Six-month period ended 2024 2023 2024 2023 Brokerage Total revenues $ 2,376.3 $ 2,088.4 $ 5,241.2 $ 4,463.6 Earnings before income taxes $ 446.3 $ 390.5 $ 1,322.4 $ 1,081.4 Identifiable assets at June 30, 2024 and 2023 $ 58,776.7 $ 50,623.8 Risk Management Total revenues $ 398.0 $ 353.6 $ 789.4 $ 684.4 Earnings before income taxes $ 65.4 $ 49.9 $ 118.6 $ 95.4 Identifiable assets at June 30, 2024 and 2023 $ 1,683.4 $ 1,212.8 Corporate Total revenues $ 1.1 $ ( 0.1 ) $ 1.5 $ — Loss before income taxes $ ( 146.1 ) $ ( 143.0 ) $ ( 302.7 ) $ ( 273.6 ) Identifiable assets at June 30, 2024 and 2023 $ 2,547.6 $ 2,528.6 Total Total revenues $ 2,775.4 $ 2,441.9 $ 6,032.1 $ 5,148.0 Earnings before income taxes $ 365.6 $ 297.4 $ 1,138.3 $ 903.2 Identifiable assets at June 30, 2024 and 2023 $ 63,007.7 $ 54,365.2 We disaggregate our revenue from contracts with clients by type and geographic location for each of our segments, as we believe it best depicts how the nature, amount, timing and uncertainty of our revenue and cash flows are affected by economic factors. Revenues by type and segment for the three-month period ended June 30, 2024 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: Commissions $ 1,661.8 $ — $ — $ 1,661.8 Fees 477.6 349.5 — 827.1 Supplemental revenues 88.7 — — 88.7 Contingent revenues 59.8 — — 59.8 Interest income, premium finance revenues and other income 88.4 9.1 1.1 98.6 Revenues before reimbursements 2,376.3 358.6 1.1 2,736.0 Reimbursements — 39.4 — 39.4 Total revenues $ 2,376.3 $ 398.0 $ 1.1 $ 2,775.4 Revenues by type and segment for the six-month period ended June 30, 2024 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: Commissions $ 3,655.4 $ — $ — $ 3,655.4 Fees 1,084.3 694.0 — 1,778.3 Supplemental revenues 182.6 — — 182.6 Contingent revenues 145.8 — — 145.8 Interest income, premium finance revenues and other income 173.1 17.4 1.5 192.0 Revenues before reimbursements 5,241.2 711.4 1.5 5,954.1 Reimbursements — 78.0 — 78.0 Total revenues $ 5,241.2 $ 789.4 $ 1.5 $ 6,032.1 Revenues by geographical location and segment for the three-month period ended June 30, 2024 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: United States $ 1,394.6 $ 324.2 $ 1.1 $ 1,719.9 United Kingdom 574.6 14.0 — 588.6 Australia 90.9 56.0 — 146.9 Canada 110.3 1.7 — 112.0 New Zealand 55.9 2.1 — 58.0 Other foreign 150.0 — — 150.0 Total revenues $ 2,376.3 $ 398.0 $ 1.1 $ 2,775.4 Revenues by geographical location and segment for the six-month period ended June 30, 2024 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: United States $ 3,208.6 $ 644.7 $ 1.5 $ 3,854.8 United Kingdom 1,159.4 28.0 — 1,187.4 Australia 158.9 109.0 — 267.9 Canada 213.4 3.4 — 216.8 New Zealand 97.6 4.3 — 101.9 Other foreign 403.3 — — 403.3 Total revenues $ 5,241.2 $ 789.4 $ 1.5 $ 6,032.1 Revenues by type and segment for the three-month period ended June 30, 2023 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: Commissions $ 1,410.4 $ — $ — $ 1,410.4 Fees 478.5 312.0 — 790.5 Supplemental revenues 71.2 — — 71.2 Contingent revenues 54.2 — — 54.2 Interest income, premium finance revenues and other income 74.1 6.6 ( 0.1 ) 80.6 Revenues before reimbursements 2,088.4 318.6 ( 0.1 ) 2,406.9 Reimbursements — 35.0 — 35.0 Total revenues $ 2,088.4 $ 353.6 $ ( 0.1 ) $ 2,441.9 Revenues by type and segment for the six-month period ended June 30, 2023 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: Commissions $ 3,157.8 $ — $ — $ 3,157.8 Fees 891.2 605.0 — 1,496.2 Supplemental revenues 152.8 — — 152.8 Contingent revenues 126.0 — — 126.0 Interest income, premium finance revenues and other income 135.8 11.2 — 147.0 Revenues before reimbursements 4,463.6 616.2 — 5,079.8 Reimbursements — 68.2 — 68.2 Total revenues $ 4,463.6 $ 684.4 $ — $ 5,148.0 Revenues by geographical location and segment for the three-month period ended June 30, 2023 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: United States $ 1,199.7 $ 298.7 $ ( 0.1 ) $ 1,498.3 United Kingdom 527.6 11.6 — 539.2 Australia 83.8 37.5 — 121.3 Canada 104.6 1.5 — 106.1 New Zealand 53.0 4.3 — 57.3 Other foreign 119.7 — — 119.7 Total revenues $ 2,088.4 $ 353.6 $ ( 0.1 ) $ 2,441.9 Revenues by geographical location and segment for the six-month period ended June 30, 2023 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: United States $ 2,675.0 $ 578.8 $ — $ 3,253.8 United Kingdom 1,041.1 22.9 — 1,064.0 Australia 148.0 71.5 — 219.5 Canada 198.3 3.0 — 201.3 New Zealand 91.0 8.2 — 99.2 Other foreign 310.2 — — 310.2 Total revenues $ 4,463.6 $ 684.4 $ — $ 5,148.0

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2024
Accounting Policies [Abstract]
Nature of Operations and Basis of Presentation	Nature of Operations and Basis of Presentation Arthur J. Gallagher & Co. and its subsidiaries, collectively referred to herein as we, our, us, Gallagher or the company, provide insurance and reinsurance brokerage, consulting and third party claims settlement and administration services to both domestic and international entities. We have three reportable segments: brokerage, risk management and corporate. Our brokers, agents and administrators act as intermediaries between underwriting enterprises and our clients. Our brokerage segment operations provide brokerage and consulting services to entities of all types, including commercial, nonprofit, public sector entities, and, to a lesser extent, individuals, in the areas of insurance and reinsurance placements, risk of loss management, and management of employer sponsored benefit programs. Our risk management segment operations provide contract claim settlement, claim administration, loss control services and risk management consulting for commercial, nonprofit, captive and public sector entities, and various other organizations that choose to self-insure property/casualty coverages or choose to use a third‑party claims management organization rather than the claim services provided by underwriting enterprises. The corporate segment reports the financial information related to our debt and other corporate costs, clean energy investments, external acquisition‑related expenses and the impact of foreign currency translation. We do not assume insurance underwriting risk on a net basis, other than with respect to de minimis amounts necessary to provide minimum or regulatory capital to organize captives, pools, specialized underwriters or risk-retention groups. Rather, capital necessary for covering losses is provided by underwriting enterprises. Interest income, premium finance revenues and other income are primarily generated from our premium financing operations, our invested cash and restricted cash we hold on behalf of our clients, as well as clean energy investments. In addition, our share of the net earnings related to partially owned entities that are accounted for using the equity method is included in other income. We are a global insurance brokerage, risk management and consulting services firm, headquartered in Rolling Meadows, Illinois. We provide these services in approximately 130 countries around the world through our owned operations and a network of correspondent brokers and consultants. We have prepared the accompanying unaudited consolidated financial statements pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in annual financial statements have been omitted pursuant to such rules and regulations. The unaudited consolidated financial statements included herein are, in the opinion of management, prepared on a basis consistent with our audited consolidated financial statements for the year ended December 31, 2023, and include all normal recurring adjustments necessary for a fair presentation of the information set forth herein. The quarterly results of operations are not necessarily indicative of the results of operations to be reported for subsequent quarters or the full year. These unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2023. In the preparation of our unaudited consolidated financial statements as of June 30, 2024 , management evaluated all material subsequent events or transactions that occurred after the balance sheet date through the date on which the financial statements were issued, for potential recognition and/or disclosure therein.
Use of Estimates	Use of Estimates The preparation of our unaudited consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. These accounting principles require us to make estimates and assumptions that affect the reported amounts of assets and liabilities and revenues and expenses, and the disclosure of contingent assets and liabilities at the date of our unaudited consolidated financial statements. We periodically evaluate our estimates and assumptions, including those relating to the valuation of goodwill and other intangible assets, right-of-use assets, investments, income taxes, revenue recognition, deferred costs, stock-based compensation, claims handling obligations, retirement plans, litigation and contingencies. We base our estimates on historical experience and various assumptions that we believe to be reasonable based on specific circumstances. Such estimates and assumptions could change in the future as more information becomes known, which could impact the amounts reported and disclosed in the notes herein.

Business Combinations (Tables)

Business Combinations (Tables)	6 Months Ended
	Jun. 30, 2024
Business Combinations [Abstract]
Acquisition Method for Recording Business Combinations	During the six-month period ended June 30, 2024, we acquired substantially all of the ownership interest or net assets, as applicable, of the following firms in exchange for our common stock and/or cash. These acquisitions have been accounted for using the acquisition method for recording business combinations (in millions, except share data): Total Maximum Common Common Recorded Recorded Potential Name and Effective Shares Share Accrued Escrow Earnout Purchase Earnout Date of Acquisition Issued Value Cash Paid Liability Deposited Payable Price Payable (000s) Ericson Insurance Services, LLC 129 $ 30.1 $ 26.5 $ — $ 3.0 $ 7.0 $ 66.6 $ 10.0 The Rowley Agency, LLC — — 117.2 — 11.0 — 128.2 — OperationsInc, LLC — $ — $ 52.6 $ — $ 2.8 $ 11.0 $ 66.4 $ 20.0 Twenty-one other acquisitions 229 48.8 271.3 2.6 16.8 53.3 392.8 108.5 358 $ 78.9 $ 467.6 $ 2.6 $ 33.6 $ 71.3 $ 654.0 $ 138.5
Summary of Estimated Fair Values of Net Assets Acquired	The following is a summary of the estimated fair values of the net assets acquired at the date of each acquisition made in the six-month period ended June 30, 2024 (in millions): Twenty-one Other EIS TRA OPR Acquisitions Total Cash and cash equivalents $ 0.1 $ 4.1 $ 0.8 $ 9.9 $ 14.9 Fiduciary assets 1.0 2.6 — 34.1 37.7 Other current assets 3.5 0.5 2.7 11.3 18.0 Fixed assets — 0.4 — 0.7 1.1 Noncurrent assets 0.1 1.7 2.0 3.8 7.6 Goodwill 27.4 65.8 41.9 205.9 341.0 Expiration lists 35.9 57.4 22.1 185.5 300.9 Non-compete agreements 0.5 0.6 0.2 6.2 7.5 Trade names — — — 0.3 0.3 Total assets acquired 68.5 133.1 69.7 457.7 729.0 Fiduciary liabilities 1.0 2.6 — 34.1 37.7 Current liabilities 0.8 0.6 1.1 14.7 17.2 Noncurrent liabilities 0.1 1.7 2.2 16.1 20.1 Total liabilities assumed 1.9 4.9 3.3 64.9 75.0 Total net assets acquired $ 66.6 $ 128.2 $ 66.4 $ 392.8 $ 654.0
Summary of Unaudited Pro Forma Historical Results	The following is a summary of the unaudited pro forma historical results, as if these entities had been acquired at January 1, 2023 (in millions, except per share data) : Three-month period ended Six-month period ended June 30, June 30, 2024 2023 2024 2023 Total revenues $ 2,785.4 $ 2,478.5 $ 6,061.9 $ 5,223.0 Net earnings attributable to controlling interests 283.9 235.8 893.7 724.9 Basic net earnings per share 1.30 1.10 4.10 3.38 Diluted net earnings per share 1.27 1.07 4.02 3.32

Contracts with Customers (Table

Contracts with Customers (Tables)	6 Months Ended
	Jun. 30, 2024
Revenue from Contract with Customer [Abstract]
Summary of Unbilled Receivables, Contract Assets and Contract Liabilities from Contracts with Customers	Information about unbilled receivables, contract assets and contract liabilities from contracts with customers is as follows (in millions): June 30, December 31, Unbilled receivables $ 1,536.6 $ 1,093.7 Deferred contract costs 123.0 169.1 Deferred revenue 762.9 706.2
Summary of Changes in Deferred Revenue Balances	Significant changes in the deferred revenue balances, which include foreign currency translation adjustments, during the period are as follows (in millions): Risk Brokerage Management Total Deferred revenue at December 31, 2023 $ 533.6 $ 172.6 $ 706.2 Incremental deferred revenue 417.5 45.5 463.0 Revenue recognized during the six-month period ended ( 343.5 ) ( 42.1 ) ( 385.6 ) Net change in collected billings/deposits received from customers ( 22.8 ) ( 0.9 ) ( 23.7 ) Impact of change in foreign exchange rates ( 2.2 ) ( 0.1 ) ( 2.3 ) Deferred revenue recognized from business acquisitions 5.3 — 5.3 Deferred revenue at June 30, 2024 $ 587.9 $ 175.0 $ 762.9
Summary of Expected Revenue Related to Performance Obligations	The estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied (or partially unsatisfied) at the end of the reporting period is as follows (in millions): Brokerage Risk Total 2024 (remaining six months) $ 504.9 $ 86.4 $ 591.3 2025 64.2 38.9 103.1 2026 16.8 17.4 34.2 2027 1.0 13.0 14.0 2028 0.5 6.8 7.3 Thereafter 0.5 12.5 13.0 Total $ 587.9 $ 175.0 $ 762.9

Intangible Assets (Tables)

Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Carrying Amount of Goodwill Allocated by Domestic and Foreign Operations	The carrying amount of goodwill at June 30, 2024 and December 31, 2023 allocated by domestic and foreign operations is as follows (in millions): Brokerage Risk Corporate Total At June 30, 2024 United States $ 6,651.7 $ 74.8 $ — $ 6,726.5 United Kingdom 2,503.1 18.4 — 2,521.5 Canada 606.8 — — 606.8 Australia 522.6 234.5 — 757.1 New Zealand 197.0 9.2 — 206.2 Other foreign 1,078.5 — 18.9 1,097.4 Total goodwill $ 11,559.7 $ 336.9 $ 18.9 $ 11,915.5 At December 31, 2023 United States $ 6,304.5 $ 74.8 $ — $ 6,379.3 United Kingdom 2,493.4 18.5 — 2,511.9 Canada 623.7 — — 623.7 Australia 514.6 135.9 — 650.5 New Zealand 204.2 9.6 — 213.8 Other foreign 1,077.4 — 19.0 1,096.4 Total goodwill $ 11,217.8 $ 238.8 $ 19.0 $ 11,475.6
Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the six-month period ended June 30, 2024 are as follows (in millions): Brokerage Risk Corporate Total Balance as of December 31, 2023 $ 11,217.8 $ 238.8 $ 19.0 $ 11,475.6 Goodwill acquired during the period 341.0 — — 341.0 Goodwill true-ups due to appraisals and other acquisition 94.4 102.0 — 196.4 Goodwill written-off related to sales of business and impairment ( 5.8 ) — — ( 5.8 ) Foreign currency translation adjustments during the period ( 87.7 ) ( 3.9 ) ( 0.1 ) ( 91.7 ) Balance as of June 30, 2024 $ 11,559.7 $ 336.9 $ 18.9 $ 11,915.5
Major Classes of Amortizable Intangible Assets	Major classes of amortizable intangible assets at June 30, 2024 and December 31, 2023 consist of the following (in millions): June 30, December 31, 2024 2023 Expiration lists $ 8,341.8 $ 8,222.8 Accumulated amortization - expiration lists ( 4,025.8 ) ( 3,733.2 ) 4,316.0 4,489.6 Non-compete agreements 103.3 112.2 Accumulated amortization - non-compete agreements ( 79.9 ) ( 74.9 ) 23.4 37.3 Trade names 119.7 171.8 Accumulated amortization - trade names ( 69.7 ) ( 65.4 ) 50.0 106.4 Net amortizable assets $ 4,389.4 $ 4,633.3
Estimated Aggregate Amortization Expense	Estimated aggregate amortization expense for each of the next five years and thereafter is as follows (in millions): 2024 (remaining six months) $ 310.1 2025 587.5 2026 544.3 2027 510.5 2028 470.1 Thereafter 1,966.9 Total $ 4,389.4

Credit and Other Debt Agreeme_2

Credit and Other Debt Agreements (Tables)	6 Months Ended
	Jun. 30, 2024
Debt Disclosure [Abstract]
Summary of Corporate and Other Debt	The following is a summary of our corporate and other debt (in millions): June 30, December 31, 2024 2023 Senior Notes: Semi-annual payments of interest, fixed rate of 2.40 %, balloon due November 9, 2031 $ 400.0 $ 400.0 Semi-annual payments of interest, fixed rate of 5.50 %, balloon due March 2, 2033 350.0 350.0 Semi-annual payments of interest, fixed rate of 6.50 %, balloon due February 15, 2034 400.0 400.0 Semi-annual payments of interest, fixed rate of 5.45 %, balloon due July 15, 2034 500.0 — Semi-annual payments of interest, fixed rate of 3.50 %, balloon due May 20, 2051 850.0 850.0 Semi-annual payments of interest, fixed rate of 3.05 %, balloon due March 9, 2052 350.0 350.0 Semi-annual payments of interest, fixed rate of 5.75 %, balloon due March 2, 2053 600.0 600.0 Semi-annual payments of interest, fixed rate of 6.75 %, balloon due February 15, 2054 600.0 600.0 Semi-annual payments of interest, fixed rate of 5.75 %, balloon due July 15, 2054 500.0 — Total Senior Notes 4,550.0 3,550.0 Note Purchase Agreements: Semi-annual payments of interest, fixed rate of 4.72 %, balloon due February 13, 2024 — 100.0 Semi-annual payments of interest, fixed rate of 4.58 %, balloon due February 27, 2024 — 325.0 Semi-annual payments of interest, fixed rate of 4.31 %, balloon due June 24, 2025 200.0 200.0 Semi-annual payments of interest, fixed rate of 4.85 %, balloon due February 13, 2026 140.0 140.0 Semi-annual payments of interest, fixed rate of 4.73 %, balloon due February 27, 2026 175.0 175.0 Semi-annual payments of interest, fixed rate of 4.40 %, balloon due June 2, 2026 175.0 175.0 Semi-annual payments of interest, fixed rate of 4.36 %, balloon due June 24, 2026 150.0 150.0 Semi-annual payments of interest, fixed rate of 3.75 %, balloon due January 30, 2027 30.0 30.0 Semi-annual payments of interest, fixed rate of 4.09 %, balloon due June 27, 2027 125.0 125.0 Semi-annual payments of interest, fixed rate of 4.09 %, balloon due August 2, 2027 125.0 125.0 Semi-annual payments of interest, fixed rate of 4.14 %, balloon due August 4, 2027 98.0 98.0 Semi-annual payments of interest, fixed rate of 3.46 %, balloon due December 1, 2027 100.0 100.0 Semi-annual payments of interest, fixed rate of 4.55 %, balloon due June 2, 2028 75.0 75.0 Semi-annual payments of interest, fixed rate of 4.34 %, balloon due June 13, 2028 125.0 125.0 Semi-annual payments of interest, fixed rate of 5.04 %, balloon due February 13, 2029 100.0 100.0 Semi-annual payments of interest, fixed rate of 4.98 %, balloon due February 27, 2029 100.0 100.0 Semi-annual payments of interest, fixed rate of 4.19 %, balloon due June 27, 2029 50.0 50.0 Semi-annual payments of interest, fixed rate of 4.19 %, balloon due August 2, 2029 50.0 50.0 Semi-annual payments of interest, fixed rate of 3.48 %, balloon due December 2, 2029 50.0 50.0 Semi-annual payments of interest, fixed rate of 3.99 %, balloon due January 30, 2030 341.0 341.0 Semi-annual payments of interest, fixed rate of 4.44 %, balloon due June 13, 2030 125.0 125.0 Semi-annual payments of interest, fixed rate of 5.14 %, balloon due March 13, 2031 180.0 180.0 Semi-annual payments of interest, fixed rate of 4.70 %, balloon due June 2, 2031 25.0 25.0 Semi-annual payments of interest, fixed rate of 4.09 %, balloon due January 30, 2032 69.0 69.0 Semi-annual payments of interest, fixed rate of 4.34 %, balloon due June 27, 2032 75.0 75.0 Semi-annual payments of interest, fixed rate of 4.34 %, balloon due August 2, 2032 75.0 75.0 Semi-annual payments of interest, fixed rate of 4.59 %, balloon due June 13, 2033 125.0 125.0 Semi-annual payments of interest, fixed rate of 5.29 %, balloon due March 13, 2034 40.0 40.0 Semi-annual payments of interest, fixed rate of 4.48 %, balloon due June 12, 2034 175.0 175.0 Semi-annual payments of interest, fixed rate of 4.24 %, balloon due January 30, 2035 79.0 79.0 Semi-annual payments of interest, fixed rate of 2.44 %, balloon due February 10, 2036 100.0 100.0 Semi-annual payments of interest, fixed rate of 2.46 %, balloon due May 5, 2036 75.0 75.0 Semi-annual payments of interest, fixed rate of 4.69 %, balloon due June 13, 2038 75.0 75.0 Semi-annual payments of interest, fixed rate of 5.45 %, balloon due March 13, 2039 40.0 40.0 Semi-annual payments of interest, fixed rate of 4.49 %, balloon due January 30, 2040 56.0 56.0 Total Note Purchase Agreements 3,523.0 3,948.0 Credit Agreement: Periodic payments of interest and principal, prime or SOFR plus up 1.075 %, expires June 22, 2028 80.0 245.0 Premium Financing Debt Facility - expires October 31, 2025 : Facility B AUD denominated tranche, interbank rates plus 1.500 % 199.6 249.0 NZD denominated tranche, interbank rates plus 1.850 % — — Facility C and D AUD denominated tranche, interbank rates plus 0.830 % — 31.4 NZD denominated tranche, interbank rates plus 0.990 % 8.2 8.6 Total Premium Financing Debt Facility 207.8 289.0 Total corporate and other debt 8,360.8 8,032.0 Less unamortized debt acquisition costs on Senior Notes and Note Purchase Agreements ( 46.8 ) ( 38.4 ) Less unamortized discount on Bonds Payable ( 35.3 ) ( 28.6 ) Net corporate and other debt $ 8,278.7 $ 7,965.0

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2024
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net EPS	The following table sets forth the computation of basic and diluted net earnings per share (in millions, except per share data): Three-month period ended Six-month period ended June 30, June 30, 2024 2023 2024 2023 Net earnings attributable to controlling interests $ 283.4 $ 234.5 $ 891.8 $ 721.0 Weighted average number of common shares outstanding 218.8 214.9 218.1 213.8 Dilutive effect of stock options using the treasury 4.1 4.1 4.3 4.2 Weighted average number of common and common 222.9 219.0 222.4 218.0 Basic net earnings per share $ 1.30 $ 1.09 $ 4.09 $ 3.37 Diluted net earnings per share $ 1.27 $ 1.07 $ 4.01 $ 3.31

Stock Option Plans (Tables)

Stock Option Plans (Tables)	6 Months Ended
	Jun. 30, 2024
Text Block [Abstract]
Black-Scholes Option Pricing Model with Weighted Average	For purposes of expense recognition, the estimated fair values of the stock option grants are amortized to expense over the options’ vesting period. We estimated the fair value of stock options at the date of grant using the Black-Scholes option pricing model with the following weighted average assumptions: 2024 2023 Expected dividend yield 1.0 % 1.2 % Expected risk-free interest rate 4.2 % 3.6 % Volatility 25.3 % 25.0 % Expected life (in years) 5.5 5.4
Stock Option Activity and Related Information	The following is a summary of our stock option activity and related information for 2024 (in millions, except exercise price and year data): Six-month period ended June 30, 2024 Weighted Average Weighted Remaining Shares Average Contractual Aggregate Under Exercise Term Intrinsic Option Price (in years) Value Beginning balance 7.9 $ 123.85 Granted 1.0 243.54 Exercised ( 1.0 ) 76.40 Forfeited or canceled ( 0.1 ) 151.05 Ending balance 7.8 $ 145.70 4.18 $ 883.9 Exercisable at end of period 2.1 $ 88.79 2.19 $ 353.9 Ending unvested and expected to vest 5.2 $ 164.50 4.86 $ 494.1
Other Information Regarding Stock Options Outstanding and Exercisable	Other information regarding stock options outstanding and exercisable at June 30, 2024 is summarized as follows (in millions, except exercise price and year data): Options Outstanding Options Exercisable Weighted Average Remaining Weighted Weighted Contractual Average Average Number Term Exercise Number Exercise Range of Exercise Prices Outstanding (in years) Price Exercisable Price $ 70.74 — $ 70.74 0.4 0.71 $ 70.74 0.4 $ 70.74 79.59 — 79.59 0.7 1.70 79.59 0.7 79.59 86.17 — 86.17 1.1 2.70 86.17 0.6 86.17 127.90 — 127.90 1.4 3.71 127.90 0.4 127.90 156.85 — 156.85 1.0 4.59 156.85 — — 158.56 — 161.14 1.1 4.72 158.65 — — 177.09 — 202.13 1.1 5.72 177.78 — — 238.88 — 243.54 1.0 6.67 243.54 — — $ 70.74 — $ 243.54 7.8 4.18 $ 145.70 2.1 $ 88.79

Derivatives and Hedging Activ_2

Derivatives and Hedging Activity (Tables)	6 Months Ended
	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Notional and Fair Values of Derivative Instruments	The notional and fair values of derivatives designated as hedging instruments are as follows at June 30, 2024 and December 31, 2023 (in millions): Derivative Assets Derivative Liabilities Notional Balance Sheet Fair Balance Sheet Fair Instrument Amount Classification Value Classification Value At June 30, 2024 Interest rate contracts $ — Other current assets $ — Accrued compensation and other current liabilities $ — Other noncurrent assets — Other noncurrent liabilities — Foreign exchange contracts (1) 46.4 Other current assets 4.9 Accrued compensation and other current liabilities 2.6 Other noncurrent assets 10.1 Other noncurrent liabilities 4.1 Total $ 46.4 $ 15.0 $ 6.7 At December 31, 2023 Interest rate contracts $ 150.0 Other current assets $ — Accrued compensation and other current liabilities $ 5.7 Other noncurrent assets — Other noncurrent liabilities — Foreign exchange contracts (1) 67.8 Other current assets 3.9 Accrued compensation and other current liabilities 3.9 Other noncurrent assets 14.2 Other noncurrent liabilities 4.0 Total $ 217.8 $ 18.1 $ 13.6 (1) Included within foreign exchange contracts at June 30, 2024 were $ 819.3 million of call options, offset with $ 819.3 million of put options, and $ 3.0 million of buy forwards, offset with $ 49.4 million of sell forwards. Included within foreign exchange contracts at December 31, 2023 were $ 331.3 million of call options, offset with $ 331.3 million of put options, and $ 5.5 million of buy forwards, offset with $ 73.3 million of sell forwards.
Summary of Amounts of Derivative Gains (Losses) Recognized In Accumulated Other Comprehensive Loss	The effect of cash flow hedge accounting on accumulated other comprehensive loss for the six-month periods ended June 30, 2024 and 2023 was as follows (in millions): Amount of Amount of Gain Gain (Loss) Recognized Amount of Reclassified in Earnings Gain (Loss) from Related to Recognized in Accumulated Amount Accumulated Other Excluded Other Comprehensive from Comprehensive Loss into Effectiveness Statement of Earnings Instrument Loss (1) Earnings Testing Classification Three-month period ended June 30, 2024 Interest rate contracts $ ( 3.6 ) $ ( 0.3 ) $ — Interest expense Foreign exchange contracts ( 0.4 ) ( 1.0 ) — Commission revenue ( 0.4 ) 0.2 Compensation expense ( 0.4 ) 0.2 Operating expense Total $ ( 4.0 ) $ ( 2.1 ) $ 0.4 Three-month period ended June 30, 2023 Interest rate contracts $ 18.9 $ ( 0.3 ) $ — Interest expense Foreign exchange contracts 12.8 0.2 — Commission revenue ( 0.5 ) 0.4 Compensation expense ( 0.4 ) 0.3 Operating expense Total $ 31.7 $ ( 1.0 ) $ 0.7 Six-month period ended June 30, 2024 Interest rate contracts $ ( 2.9 ) $ ( 0.6 ) $ — Interest expense Foreign exchange contracts ( 3.8 ) ( 0.8 ) — Commission revenue ( 0.9 ) 0.5 Compensation expense ( 0.7 ) 0.4 Operating expense Total $ ( 6.7 ) $ ( 3.0 ) $ 0.9 Six-month period ended June 30, 2023 Interest rate contracts $ 8.8 $ ( 0.6 ) $ — Interest expense Foreign exchange contracts 28.7 0.8 — Commission revenue ( 1.0 ) 1.0 Compensation expense ( 0.7 ) 0.7 Operating expense Total $ 37.5 $ ( 1.5 ) $ 1.7 (1) For the three and six-month periods ended June 30, 2024 , the amount excluded from the assessment of hedge effectiveness for our foreign exchange contracts recognized in accumulated other comprehensive loss was a loss of $ 0.1 million and a gain of $ 0.2 million, respectively. For the three and six-month periods ended June 30, 2023 , the amount excluded from the assessment of hedge effectiveness for our foreign exchange contracts recognized in accumulated other comprehensive loss was a gain of $ 0.3 million and $ 0.8 million, respectively.

Commitments, Contingencies an_2

Commitments, Contingencies and Off-Balance Sheet Arrangements (Tables)	6 Months Ended
	Jun. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Contractual Obligations	Our future minimum cash payments, including interest, associated with our contractual obligations pursuant to the Senior Notes, Note Purchase Agreements, Credit Agreement, Premium Financing Debt Facility, operating leases and purchase obligations at June 30, 2024 were as follows (in millions): Payments Due by Period Contractual Obligations 2024 2025 2026 2027 2028 Thereafter Total Senior Notes $ — $ — $ — $ — $ — $ 4,550.0 $ 4,550.0 Note Purchase Agreements — 200.0 640.0 478.0 200.0 2,005.0 3,523.0 Credit Agreement 80.0 — — — — — 80.0 Premium Financing Debt Facility 207.8 — — — — — 207.8 Interest on debt 184.4 374.0 355.0 336.7 317.2 4,285.8 5,853.1 Total debt obligations 472.2 574.0 995.0 814.7 517.2 10,840.8 14,213.9 Operating lease obligations 54.2 108.9 90.5 73.3 55.8 92.4 475.1 Less sublease arrangements ( 1.2 ) ( 1.8 ) ( 1.7 ) ( 1.6 ) ( 1.1 ) ( 0.8 ) ( 8.2 ) Outstanding purchase obligations 80.0 71.6 29.0 23.3 16.9 48.3 269.1 Total contractual obligations $ 605.2 $ 752.7 $ 1,112.8 $ 909.7 $ 588.8 $ 10,980.7 $ 14,949.9
Off-Balance Sheet Commitments	Off-Balance Sheet Commitments - Our total unrecorded commitments associated with outstanding letters of credit, and financial guarantees as of June 30, 2024 were as follows (in millions): Total Amount of Commitment Expiration by Period Amounts Off-Balance Sheet Commitments 2024 2025 2026 2027 2028 Thereafter Committed Letters of credit $ — $ — $ — $ — $ — $ 23.7 $ 23.7 Financial guarantees 1.0 — — — — — 1.0 Total commitments $ 1.0 $ — $ — $ — $ — $ 23.7 $ 24.7

Supplemental Disclosures of C_2

Supplemental Disclosures of Cash Flow Information (Tables)	6 Months Ended
	Jun. 30, 2024
Cash and Cash Equivalents [Abstract]
Supplemental Disclosures of Cash Flow Information	Six-month period ended June 30, Supplemental disclosures of cash flow information (in millions): 2024 2023 Interest paid $ 162.1 $ 127.3 Income taxes paid, net 167.8 116.7
Summary of Cash, Cash Equivalents, Restricted Cash and Fiduciary Cash	The following is a reconciliation of our end of period cash, cash equivalents, restricted cash and fiduciary cash balances as presented in the consolidated statement of cash flows for the six-month periods ended June 30, 2024 and 2023 (in millions): June 30, 2024 2023 Cash and cash equivalents - non-restricted cash $ 1,219.2 $ 777.9 Cash and cash equivalents - restricted cash 196.1 174.4 Total cash and cash equivalents 1,415.3 952.3 Fiduciary cash 5,422.5 5,989.9 Total cash, cash equivalents, restricted cash and fiduciary cash $ 6,837.8 $ 6,942.2

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	6 Months Ended
	Jun. 30, 2024
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Loss Attributable to Controlling Interests	The after-tax components of our accumulated other comprehensive loss attributable to controlling interests consist of the following (in millions): Foreign Fair Value of Accumulated Pension Currency Derivative Comprehensive Liability Translation Investments Loss Balance as of December 31, 2023 $ ( 37.1 ) $ ( 867.4 ) $ 112.4 $ ( 792.1 ) Net change in period 0.2 ( 144.5 ) ( 2.8 ) ( 147.1 ) Balance as of June 30, 2024 $ ( 36.9 ) $ ( 1,011.9 ) $ 109.6 $ ( 939.2 )

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2024
Segment Reporting [Abstract]
Schedule of Segment Reporting Information by Segment	Financial information relating to our segments for the three and six-month periods ended June 30, 2024 and 2023 as follows (in millions): Three-month period ended Six-month period ended 2024 2023 2024 2023 Brokerage Total revenues $ 2,376.3 $ 2,088.4 $ 5,241.2 $ 4,463.6 Earnings before income taxes $ 446.3 $ 390.5 $ 1,322.4 $ 1,081.4 Identifiable assets at June 30, 2024 and 2023 $ 58,776.7 $ 50,623.8 Risk Management Total revenues $ 398.0 $ 353.6 $ 789.4 $ 684.4 Earnings before income taxes $ 65.4 $ 49.9 $ 118.6 $ 95.4 Identifiable assets at June 30, 2024 and 2023 $ 1,683.4 $ 1,212.8 Corporate Total revenues $ 1.1 $ ( 0.1 ) $ 1.5 $ — Loss before income taxes $ ( 146.1 ) $ ( 143.0 ) $ ( 302.7 ) $ ( 273.6 ) Identifiable assets at June 30, 2024 and 2023 $ 2,547.6 $ 2,528.6 Total Total revenues $ 2,775.4 $ 2,441.9 $ 6,032.1 $ 5,148.0 Earnings before income taxes $ 365.6 $ 297.4 $ 1,138.3 $ 903.2 Identifiable assets at June 30, 2024 and 2023 $ 63,007.7 $ 54,365.2
Summary of Revenues by Type and Segment	Revenues by type and segment for the three-month period ended June 30, 2024 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: Commissions $ 1,661.8 $ — $ — $ 1,661.8 Fees 477.6 349.5 — 827.1 Supplemental revenues 88.7 — — 88.7 Contingent revenues 59.8 — — 59.8 Interest income, premium finance revenues and other income 88.4 9.1 1.1 98.6 Revenues before reimbursements 2,376.3 358.6 1.1 2,736.0 Reimbursements — 39.4 — 39.4 Total revenues $ 2,376.3 $ 398.0 $ 1.1 $ 2,775.4 Revenues by type and segment for the six-month period ended June 30, 2024 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: Commissions $ 3,655.4 $ — $ — $ 3,655.4 Fees 1,084.3 694.0 — 1,778.3 Supplemental revenues 182.6 — — 182.6 Contingent revenues 145.8 — — 145.8 Interest income, premium finance revenues and other income 173.1 17.4 1.5 192.0 Revenues before reimbursements 5,241.2 711.4 1.5 5,954.1 Reimbursements — 78.0 — 78.0 Total revenues $ 5,241.2 $ 789.4 $ 1.5 $ 6,032.1 Revenues by type and segment for the three-month period ended June 30, 2023 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: Commissions $ 1,410.4 $ — $ — $ 1,410.4 Fees 478.5 312.0 — 790.5 Supplemental revenues 71.2 — — 71.2 Contingent revenues 54.2 — — 54.2 Interest income, premium finance revenues and other income 74.1 6.6 ( 0.1 ) 80.6 Revenues before reimbursements 2,088.4 318.6 ( 0.1 ) 2,406.9 Reimbursements — 35.0 — 35.0 Total revenues $ 2,088.4 $ 353.6 $ ( 0.1 ) $ 2,441.9 Revenues by type and segment for the six-month period ended June 30, 2023 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: Commissions $ 3,157.8 $ — $ — $ 3,157.8 Fees 891.2 605.0 — 1,496.2 Supplemental revenues 152.8 — — 152.8 Contingent revenues 126.0 — — 126.0 Interest income, premium finance revenues and other income 135.8 11.2 — 147.0 Revenues before reimbursements 4,463.6 616.2 — 5,079.8 Reimbursements — 68.2 — 68.2 Total revenues $ 4,463.6 $ 684.4 $ — $ 5,148.0
Summary of Geographical Location and Segment	Revenues by geographical location and segment for the three-month period ended June 30, 2024 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: United States $ 1,394.6 $ 324.2 $ 1.1 $ 1,719.9 United Kingdom 574.6 14.0 — 588.6 Australia 90.9 56.0 — 146.9 Canada 110.3 1.7 — 112.0 New Zealand 55.9 2.1 — 58.0 Other foreign 150.0 — — 150.0 Total revenues $ 2,376.3 $ 398.0 $ 1.1 $ 2,775.4 Revenues by geographical location and segment for the six-month period ended June 30, 2024 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: United States $ 3,208.6 $ 644.7 $ 1.5 $ 3,854.8 United Kingdom 1,159.4 28.0 — 1,187.4 Australia 158.9 109.0 — 267.9 Canada 213.4 3.4 — 216.8 New Zealand 97.6 4.3 — 101.9 Other foreign 403.3 — — 403.3 Total revenues $ 5,241.2 $ 789.4 $ 1.5 $ 6,032.1 Revenues by geographical location and segment for the three-month period ended June 30, 2023 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: United States $ 1,199.7 $ 298.7 $ ( 0.1 ) $ 1,498.3 United Kingdom 527.6 11.6 — 539.2 Australia 83.8 37.5 — 121.3 Canada 104.6 1.5 — 106.1 New Zealand 53.0 4.3 — 57.3 Other foreign 119.7 — — 119.7 Total revenues $ 2,088.4 $ 353.6 $ ( 0.1 ) $ 2,441.9 Revenues by geographical location and segment for the six-month period ended June 30, 2023 are as follows (in millions): Risk Brokerage Management Corporate Total Revenues: United States $ 2,675.0 $ 578.8 $ — $ 3,253.8 United Kingdom 1,041.1 22.9 — 1,064.0 Australia 148.0 71.5 — 219.5 Canada 198.3 3.0 — 201.3 New Zealand 91.0 8.2 — 99.2 Other foreign 310.2 — — 310.2 Total revenues $ 4,463.6 $ 684.4 $ — $ 5,148.0

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2024 Country Segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | Segment	3
Number of countries in which the company does business through a network of correspondent brokers and consultants | Country	130

Business Combinations - Acquisi

Business Combinations - Acquisition Method for Recording Business Combinations (Detail) shares in Thousands	6 Months Ended
	Jun. 30, 2024 USD ($) shares
Ericson Insurance Services [Member]
Business Acquisition [Line Items]
Common Shares Issued | shares	129
Common Share Value	$ 30,100,000
Cash Paid	26,500,000
Escrow Deposited	3,000,000
Recorded Earnout Payable	7,000,000
Total Recorded Purchase Price	66,600,000
Maximum Potential Earnout Payable	10,000,000
The Rowley Agency [Member]
Business Acquisition [Line Items]
Cash Paid	117,200,000
Escrow Deposited	11,000,000
Total Recorded Purchase Price	128,200,000
OperationsInc [Member]
Business Acquisition [Line Items]
Cash Paid	52,600,000
Escrow Deposited	2,800,000
Recorded Earnout Payable	11,000,000
Total Recorded Purchase Price	66,400,000
Maximum Potential Earnout Payable	$ 20,000,000
Twenty-One Other Acquisitions [Member]
Business Acquisition [Line Items]
Common Shares Issued | shares	229
Common Share Value	$ 48,800,000
Cash Paid	271,300,000
Accrued Liability	2,600,000
Escrow Deposited	16,800,000
Recorded Earnout Payable	53,300,000
Total Recorded Purchase Price	392,800,000
Maximum Potential Earnout Payable	$ 108,500,000
2024 Acquisitions [Member]
Business Acquisition [Line Items]
Common Shares Issued | shares	358
Common Share Value	$ 78,900,000
Cash Paid	467,600,000
Accrued Liability	2,600,000
Escrow Deposited	33,600,000
Recorded Earnout Payable	71,300,000
Total Recorded Purchase Price	654,000,000
Maximum Potential Earnout Payable	$ 138,500,000

Business Combinations - Additio

Business Combinations - Additional Information (Detail) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended	270 Months Ended
	Jun. 30, 2024 USD ($) Entity	Jun. 30, 2023 USD ($) Entity	Jun. 30, 2024 USD ($) Entity	Jun. 30, 2023 USD ($) Entity	Dec. 31, 2023 USD ($)	Jun. 30, 2024 USD ($) Entity
Business Acquisition [Line Items]
Accretion of the discount on acquisition	$ 15	$ 19.8	$ 33.8	$ 39.6
Income (expense) related to net adjustments to estimated fair value of liability for earnout obligations	$ (3.8)	$ 10.4	$ 31.1	$ (11.6)
Number of companies acquired | Entity	30	34	58	45		725
Aggregate amount of maximum earnout obligations related to acquisitions			$ 1,925.8
Aggregate amount of maximum earnout obligations related to acquisitions, recorded in consolidated balance sheet			1,236.7
Aggregate amount of earnout obligation expected settlement in cash or stock at option	$ 491.8		491.8			$ 491.8
Aggregate amount of earnout obligation expected settlement in cash	744.9		744.9			744.9
Goodwill	341		341			341
Expiration lists	300.9		300.9			300.9
Non-compete agreements	7.5		7.5			7.5
Trade names	0.3		0.3			0.3
Net increase to goodwill			196.4		$ 256.7
Total revenues	2,785.4	$ 2,478.5	6,061.9	$ 5,223
Brokerage and Risk Management [Member]
Business Acquisition [Line Items]
Write-off of amortizable intangible assets		$ 3.1		$ 3.2
Brokerage [Member]
Business Acquisition [Line Items]
Net increase to goodwill			94.4
Write-off of amortizable intangible assets	14		14
Brokerage [Member] | Expiration Lists [Member]
Business Acquisition [Line Items]
Business acquisition not deductible for income tax purposes	52.1		52.1			52.1
Brokerage [Member] | Non-Compete Agreements [Member]
Business Acquisition [Line Items]
Business acquisition not deductible for income tax purposes	4.1		4.1			4.1
Brokerage [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Business acquisition not deductible for income tax purposes	$ 0.3		$ 0.3			$ 0.3
Minimum [Member] | Expiration Lists [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years	2 years		2 years			2 years
Minimum [Member] | Non-Compete Agreements [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years	2 years		2 years			2 years
Minimum [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years	2 years		2 years			2 years
Maximum [Member] | Expiration Lists [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years	15 years		15 years			15 years
Maximum [Member] | Non-Compete Agreements [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years	6 years		6 years			6 years
Maximum [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years	15 years		15 years			15 years
2024 Acquisitions [Member] | Valuation, Market Approach [Member] | Measurement Input, Discount Rate [Member] | Minimum [Member]
Business Acquisition [Line Items]
Measurement input	0.05		0.05			0.05
2024 Acquisitions [Member] | Valuation, Market Approach [Member] | Measurement Input, Discount Rate [Member] | Maximum [Member]
Business Acquisition [Line Items]
Measurement input	0.15		0.15			0.15
2024 Acquisitions [Member] | Valuation, Income Approach | Measurement Input, Discount Rate [Member]
Business Acquisition [Line Items]
Measurement input	0.09		0.09			0.09
2023 Acquisitions [Member] | Valuation, Market Approach [Member] | Measurement Input, Long-term Revenue Growth Rate [Member] | Minimum [Member]
Business Acquisition [Line Items]
Measurement input	0.007		0.007			0.007
2023 Acquisitions [Member] | Valuation, Market Approach [Member] | Measurement Input, Long-term Revenue Growth Rate [Member] | Maximum [Member]
Business Acquisition [Line Items]
Measurement input	0.053		0.053			0.053
2023 Acquisitions [Member] | Valuation, Income Approach | Minimum [Member]
Business Acquisition [Line Items]
Attrition rate			5%
2023 Acquisitions [Member] | Valuation, Income Approach | Maximum [Member]
Business Acquisition [Line Items]
Attrition rate			11%
2023 Acquisitions [Member] | Valuation, Income Approach | Measurement Input, Long-term Revenue Growth Rate [Member] | Minimum [Member]
Business Acquisition [Line Items]
Measurement input	0.095		0.095			0.095
2023 Acquisitions [Member] | Valuation, Income Approach | Measurement Input, Long-term Revenue Growth Rate [Member] | Maximum [Member]
Business Acquisition [Line Items]
Measurement input	0.11		0.11			0.11
Business Acquisition [Member]
Business Acquisition [Line Items]
Annualized revenue of business acquisitions			$ 141.2
Total revenues			42.8
Net earnings			(5)
Net earnings before interest, income taxes, depreciation, amortization and change in estimated acquisition earnout payables			7.4
Business Acquisition [Member] | Brokerage [Member]
Business Acquisition [Line Items]
Expiration lists	$ 300.9		300.9			$ 300.9
Non-compete agreements	7.5		7.5			7.5
Trade names	0.3		0.3			0.3
Deferred tax liability	$ 13.1		$ 13.1			$ 13.1

Business Combinations - Summary

Business Combinations - Summary of Estimated Fair Values of Net Assets Acquired (Detail) $ in Millions	Jun. 30, 2024 USD ($)
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash and cash equivalents	$ 14.9
Fiduciary assets	37.7
Other current assets	18
Fixed assets	1.1
Noncurrent assets	7.6
Goodwill	341
Expiration lists	300.9
Non-compete agreements	7.5
Trade names	0.3
Total assets acquired	729
Fiduciary liabilities	37.7
Current liabilities	17.2
Noncurrent liabilities	20.1
Total liabilities assumed	75
Total net assets acquired	654
Ericson Insurance Services [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash and cash equivalents	0.1
Fiduciary assets	1
Other current assets	3.5
Noncurrent assets	0.1
Goodwill	27.4
Expiration lists	35.9
Non-compete agreements	0.5
Total assets acquired	68.5
Fiduciary liabilities	1
Current liabilities	0.8
Noncurrent liabilities	0.1
Total liabilities assumed	1.9
Total net assets acquired	66.6
The Rowley Agency [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash and cash equivalents	4.1
Fiduciary assets	2.6
Other current assets	0.5
Fixed assets	0.4
Noncurrent assets	1.7
Goodwill	65.8
Expiration lists	57.4
Non-compete agreements	0.6
Total assets acquired	133.1
Fiduciary liabilities	2.6
Current liabilities	0.6
Noncurrent liabilities	1.7
Total liabilities assumed	4.9
Total net assets acquired	128.2
OPR [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash and cash equivalents	0.8
Fiduciary assets	0
Other current assets	2.7
Fixed assets	0
Noncurrent assets	2
Goodwill	41.9
Expiration lists	22.1
Non-compete agreements	0.2
Total assets acquired	69.7
Fiduciary liabilities	0
Current liabilities	1.1
Noncurrent liabilities	2.2
Total liabilities assumed	3.3
Total net assets acquired	66.4
Twenty One Other Acquisitions [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash and cash equivalents	9.9
Fiduciary assets	34.1
Other current assets	11.3
Fixed assets	0.7
Noncurrent assets	3.8
Goodwill	205.9
Expiration lists	185.5
Non-compete agreements	6.2
Trade names	0.3
Total assets acquired	457.7
Fiduciary liabilities	34.1
Current liabilities	14.7
Noncurrent liabilities	16.1
Total liabilities assumed	64.9
Total net assets acquired	$ 392.8

Business Combinations - Summa_2

Business Combinations - Summary of Unaudited Pro Forma Historical Results (Detail) - 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 Combinations [Abstract]
Total revenues	$ 2,785.4	$ 2,478.5	$ 6,061.9	$ 5,223
Net earnings attributable to controlling interests	$ 283.9	$ 235.8	$ 893.7	$ 724.9
Basic net earnings per share	$ 1.3	$ 1.1	$ 4.1	$ 3.38
Diluted net earnings per share	$ 1.27	$ 1.07	$ 4.02	$ 3.32

Contracts with Customers - Summ

Contracts with Customers - Summary of Unbilled Receivables, Contract Assets and Contract Liabilities from Contracts with Customers (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Abstract]
Unbilled receivables	$ 1,536.6	$ 1,093.7
Deferred contract costs	123	169.1
Deferred revenue	$ 762.9	$ 706.2

Contracts with Customers - Su_2

Contracts with Customers - Summary of Changes in Deferred Revenue Balances (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2024 USD ($)
Deferred Revenue Arrangement [Line Items]
Deferred revenue beginning balance	$ 706.2
Incremental deferred revenue	463
Revenue recognized during the six-month period ended June 30, 2024 included in deferred revenue at December 31, 2023	(385.6)
Net change in collected billings/deposits received from customers	(23.7)
Impact of change in foreign exchange rates	(2.3)
Deferred revenue recognized from business acquisitions	5.3
Deferred revenue ending balance	762.9
Brokerage [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue beginning balance	533.6
Incremental deferred revenue	417.5
Revenue recognized during the six-month period ended June 30, 2024 included in deferred revenue at December 31, 2023	(343.5)
Net change in collected billings/deposits received from customers	(22.8)
Impact of change in foreign exchange rates	(2.2)
Deferred revenue recognized from business acquisitions	5.3
Deferred revenue ending balance	587.9
Risk Management [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue beginning balance	172.6
Incremental deferred revenue	45.5
Revenue recognized during the six-month period ended June 30, 2024 included in deferred revenue at December 31, 2023	(42.1)
Net change in collected billings/deposits received from customers	(0.9)
Impact of change in foreign exchange rates	(0.1)
Deferred revenue ending balance	$ 175

Contracts with Customers - Addi

Contracts with Customers - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Revenue from Contract with Customer [Abstract]
Remaining performance obligations	$ 762.9
Deferred contract costs	123	$ 169.1
Amortization of deferred contract costs	$ 362.9		$ 306.7

Contracts with Customers - Su_3

Contracts with Customers - Summary of Expected Revenue Related to Performance Obligations (Detail) $ in Millions	Jun. 30, 2024 USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 762.9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-07-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 591.3
Remaining performance obligation, expected timing of satisfaction, period	6 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 103.1
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2026-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 34.2
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2027-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 14
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2028-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 7.3
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2029-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 13
Remaining performance obligation, expected timing of satisfaction, period
Brokerage [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 587.9
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-07-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 504.9
Remaining performance obligation, expected timing of satisfaction, period	6 months
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 64.2
Remaining performance obligation, expected timing of satisfaction, period	1 year
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2026-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 16.8
Remaining performance obligation, expected timing of satisfaction, period	1 year
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2027-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 1
Remaining performance obligation, expected timing of satisfaction, period	1 year
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2028-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 0.5
Remaining performance obligation, expected timing of satisfaction, period	1 year
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2029-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 0.5
Remaining performance obligation, expected timing of satisfaction, period
Risk Management [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 175
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-07-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 86.4
Remaining performance obligation, expected timing of satisfaction, period	6 months
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 38.9
Remaining performance obligation, expected timing of satisfaction, period	1 year
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2026-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 17.4
Remaining performance obligation, expected timing of satisfaction, period	1 year
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2027-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 13
Remaining performance obligation, expected timing of satisfaction, period	1 year
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2028-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 6.8
Remaining performance obligation, expected timing of satisfaction, period	1 year
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2029-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 12.5
Remaining performance obligation, expected timing of satisfaction, period

Contracts with Customers - Su_4

Contracts with Customers - Summary of Expected Revenue Related to Performance Obligations 1 (Detail) $ in Millions	Jun. 30, 2024 USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 762.9
Brokerage [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	587.9
Risk Management [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 175

Intangible Assets - Carrying Am

Intangible Assets - Carrying Amount of Goodwill Allocated by Domestic and Foreign Operations (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Goodwill [Line Items]
Total goodwill	$ 11,915.5	$ 11,475.6
Unites States [Member]
Goodwill [Line Items]
Total goodwill	6,726.5	6,379.3
United Kingdom [Member]
Goodwill [Line Items]
Total goodwill	2,521.5	2,511.9
Canada [Member]
Goodwill [Line Items]
Total goodwill	606.8	623.7
Australia [Member]
Goodwill [Line Items]
Total goodwill	757.1	650.5
New Zealand [Member]
Goodwill [Line Items]
Total goodwill	206.2	213.8
Other Foreign [Member]
Goodwill [Line Items]
Total goodwill	1,097.4	1,096.4
Brokerage [Member]
Goodwill [Line Items]
Total goodwill	11,559.7	11,217.8
Risk Management [Member]
Goodwill [Line Items]
Total goodwill	336.9	238.8
Corporate [Member]
Goodwill [Line Items]
Total goodwill	18.9	19
Operating Segments [Member] | Brokerage [Member]
Goodwill [Line Items]
Total goodwill	11,559.7	11,217.8
Operating Segments [Member] | Brokerage [Member] | Unites States [Member]
Goodwill [Line Items]
Total goodwill	6,651.7	6,304.5
Operating Segments [Member] | Brokerage [Member] | United Kingdom [Member]
Goodwill [Line Items]
Total goodwill	2,503.1	2,493.4
Operating Segments [Member] | Brokerage [Member] | Canada [Member]
Goodwill [Line Items]
Total goodwill	606.8	623.7
Operating Segments [Member] | Brokerage [Member] | Australia [Member]
Goodwill [Line Items]
Total goodwill	522.6	514.6
Operating Segments [Member] | Brokerage [Member] | New Zealand [Member]
Goodwill [Line Items]
Total goodwill	197	204.2
Operating Segments [Member] | Brokerage [Member] | Other Foreign [Member]
Goodwill [Line Items]
Total goodwill	1,078.5	1,077.4
Operating Segments [Member] | Risk Management [Member]
Goodwill [Line Items]
Total goodwill	336.9	238.8
Operating Segments [Member] | Risk Management [Member] | Unites States [Member]
Goodwill [Line Items]
Total goodwill	74.8	74.8
Operating Segments [Member] | Risk Management [Member] | United Kingdom [Member]
Goodwill [Line Items]
Total goodwill	18.4	18.5
Operating Segments [Member] | Risk Management [Member] | Australia [Member]
Goodwill [Line Items]
Total goodwill	234.5	135.9
Operating Segments [Member] | Risk Management [Member] | New Zealand [Member]
Goodwill [Line Items]
Total goodwill	9.2	9.6
Operating Segments [Member] | Corporate [Member]
Goodwill [Line Items]
Total goodwill	18.9	19
Operating Segments [Member] | Corporate [Member] | Other Foreign [Member]
Goodwill [Line Items]
Total goodwill	$ 18.9	$ 19

Intangible Assets - Changes in

Intangible Assets - Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Goodwill [Line Items]
Beginning Balance	$ 11,475.6
Goodwill acquired during the period	341
Goodwill true-ups due to appraisals and other acquisition adjustments (see Note 3)	196.4	$ 256.7
Goodwill written-off related to sales of business and impairment	(5.8)
Foreign currency translation adjustments during the period	(91.7)
Ending Balance	11,915.5	11,475.6
Brokerage [Member]
Goodwill [Line Items]
Beginning Balance	11,217.8
Goodwill acquired during the period	341
Goodwill true-ups due to appraisals and other acquisition adjustments (see Note 3)	94.4
Goodwill written-off related to sales of business and impairment	(5.8)
Foreign currency translation adjustments during the period	(87.7)
Ending Balance	11,559.7	11,217.8
Risk Management [Member]
Goodwill [Line Items]
Beginning Balance	238.8
Goodwill true-ups due to appraisals and other acquisition adjustments (see Note 3)	102
Foreign currency translation adjustments during the period	(3.9)
Ending Balance	336.9	238.8
Corporate [Member]
Goodwill [Line Items]
Beginning Balance	19
Foreign currency translation adjustments during the period	(0.1)
Ending Balance	$ 18.9	$ 19

Intangible Assets - Major Class

Intangible Assets - Major Classes of Amortizable Intangible Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, net	$ 4,389.4	$ 4,633.3
Expiration Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	8,341.8	8,222.8
Accumulated amortization	(4,025.8)	(3,733.2)
Amortizable intangible assets, net	4,316	4,489.6
Non-Compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	103.3	112.2
Accumulated amortization	(79.9)	(74.9)
Amortizable intangible assets, net	23.4	37.3
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	119.7	171.8
Accumulated amortization	(69.7)	(65.4)
Amortizable intangible assets, net	$ 50	$ 106.4

Intangible Assets - Estimated A

Intangible Assets - Estimated Aggregate Amortization Expense (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
2024 (remaining three months)	$ 310.1
2025	587.5
2026	544.3
2027	510.5
2028	470.1
Thereafter	1,966.9
Amortizable intangible assets, net	$ 4,389.4	$ 4,633.3

Credit and Other Debt Agreeme_3

Credit and Other Debt Agreements - Summary of Corporate and Other Debt (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Semi-annual payments of interest	$ 8,360.8	$ 8,032
Less unamortized debt acquisition costs on Senior Notes and Note Purchase Agreements	(46.8)	(38.4)
Less unamortized discount on Bonds Payable	(35.3)	(28.6)
Semi-annual payments of interest, Net	8,278.7	7,965
Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	3,523	3,948
Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	4,550	3,550
Fixed Rate of 2.40%, Balloon Due November 9, 2031 [Member] | Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	400	400
Fixed Rate of 5.50%, Balloon Due March 2, 2033 [Member] | Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	350	350
Fixed Rate of 6.50%, Balloon due February 15, 2034 [Member] | Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	400	400
Fixed Rate of 5.45%, Balloon Due July 15, 2034 [Member] | Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	500
Fixed Rate of 3.50%, Balloon Due May 20, 2051 [Member] | Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	850	850
Fixed Rate of 3.05%, Balloon Due March 9, 2052 [Member] | Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	350	350
Fixed Rate of 5.75%, Balloon Due March 2, 2053 [Member] | Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	600	600
Fixed Rate of 6.75%, Balloon Due February 15, 2054 [Member] | Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	600	600
Fixed Rate of 5.75%, Balloon Due July 15, 2054 [Member] | Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	500
Fixed Rate of 4.72%, Balloon due February 13, 2024 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest		100
Fixed Rate of 4.58%, Balloon Due February 27, 2024 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest		325
Fixed Rate of 4.31%, Balloon Due June 24, 2025 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	200	200
Fixed Rate of 4.85%, Balloon due February 13, 2026 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	140	140
Fixed Rate of 4.73%, Balloon Due February 27, 2026 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	175	175
Fixed Rate of 4.40%, Balloon Due June 2, 2026 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	175	175
Fixed Rate of 4.36%, Balloon Due June 24, 2026 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	150	150
Fixed Rate of 3.75%, Balloon Due January 30, 2027 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	30	30
Fixed Rate of 4.09%, Balloon Due June 27, 2027 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	125	125
Fixed Rate of 4.09%, Balloon Due August 2, 2027 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	125	125
Fixed Rate of 4.14%, Balloon Due August 4, 2027 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	98	98
Fixed Rate of 3.46%, Balloon Due December 1, 2027 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	100	100
Fixed Rate of 4.55%, Balloon Due June 2, 2028 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	75	75
Fixed Rate of 4.34%, Balloon due June 13, 2028 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	125	125
Fixed Rate of 5.04%, Balloon due February 13, 2029 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	100	100
Fixed Rate of 4.98%, Balloon Due February 27, 2029 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	100	100
Fixed Rate of 4.19%, Balloon Due June 27, 2029 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	50	50
Fixed Rate of 4.19%, Balloon Due August 2, 2029 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	50	50
Fixed Rate of 3.48%, Balloon Due December 2, 2029 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	50	50
Fixed Rate of 3.99%, Balloon Due January 30, 2030 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	341	341
Fixed Rate of 4.44%, Balloon Due June 13, 2030 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	125	125
Fixed Rate of 5.14%, Balloon due March 13, 2031 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	180	180
Fixed Rate of 4.70%, Balloon Due June 2, 2031 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	25	25
Fixed Rate of 4.09%, Balloon Due January 30, 2032 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	69	69
Fixed Rate of 4.34%, Balloon Due June 27, 2032 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	75	75
Fixed Rate of 4.34%, Balloon Due August 2, 2032 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	75	75
Fixed Rate of 4.59%, Balloon due June 13, 2033 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	125	125
Fixed Rate of 5.29%, balloon due March 13, 2034 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	40	40
Fixed Rate of 4.48%, Balloon Due June 12, 2034 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	175	175
Fixed Rate of 4.24%, Balloon Due January 30, 2035 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	79	79
Fixed Rate of 2.44%, Balloon Due February 10, 2036 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	100	100
Fixed Rate of 2.46%, Balloon Due May 5, 2036 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	75	75
Fixed Rate of 4.69%, Balloon Due June 13, 2038 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	75	75
Fixed Rate of 5.45%, balloon due March 13, 2039 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	40	40
Fixed Rate of 4.49%, Balloon Due January 30, 2040 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	56	56
Prime or SOFR Plus up to 1.075%, Expires June 22, 2028 [Member] | Unsecured Multicurrency Credit Agreement [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	80	245
Interbank rates plus 1.500% Expires October 31, 2025 [Member] | AUD Denominated Tranche [Member] | Facility B [Member] | Premium Financing Debt Facility [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	199.6	249
Interbank Rates Plus 0.830% Expires October 31, 2025 [Member] | AUD Denominated Tranche [Member] | Facility C and D [Member] | Premium Financing Debt Facility [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest		31.4
Interbank Rates Plus 0.990% Expires October 31, 2025 [Member] | NZD Denominated Tranche [Member] | Facility C and D [Member] | Premium Financing Debt Facility [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	8.2	8.6
Interbank Rates Expires October 31, 2025 [Member] | Premium Financing Debt Facility [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	$ 207.8	$ 289

Credit and Other Debt Agreeme_4

Credit and Other Debt Agreements - Summary of Corporate and Other Debt (Parenthetical) (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Premium Financing Debt Facility [Member]
Debt Instrument [Line Items]
Periodic payments of interest and principal, expiry date	Oct. 31, 2025	Oct. 31, 2025
Fixed Rate of 2.40%, Balloon Due November 9, 2031 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	2.40%	2.40%
Periodic payments of interest and principal, expiry date	Nov. 09, 2031	Nov. 09, 2031
Fixed Rate of 5.50%, Balloon Due March 2, 2033 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	5.50%	5.50%
Periodic payments of interest and principal, expiry date	Mar. 02, 2033	Mar. 02, 2033
Fixed Rate of 6.50%, Balloon due February 15, 2034 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	6.50%	6.50%
Periodic payments of interest and principal, expiry date	Feb. 15, 2034	Feb. 15, 2034
Fixed Rate of 5.45%, Balloon Due July 15, 2034 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	5.45%	5.45%
Periodic payments of interest and principal, expiry date	Jul. 15, 2034	Jul. 15, 2034
Fixed Rate of 3.50%, Balloon Due May 20, 2051 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	3.50%	3.50%
Periodic payments of interest and principal, expiry date	May 20, 2051	May 20, 2051
Fixed Rate of 3.05%, Balloon Due March 9, 2052 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	3.05%	3.05%
Periodic payments of interest and principal, expiry date	Mar. 09, 2052	Mar. 09, 2052
Fixed Rate of 6.75%, Balloon Due February 15, 2054 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	6.75%	6.75%
Periodic payments of interest and principal, expiry date	Feb. 15, 2054	Feb. 15, 2054
Fixed Rate of 5.75%, Balloon Due July 15, 2054 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	5.75%	5.75%
Periodic payments of interest and principal, expiry date	Jul. 15, 2054	Jul. 15, 2054
Fixed Rate of 5.75%, Balloon Due March 2, 2053 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	5.75%	5.75%
Periodic payments of interest and principal, expiry date	Mar. 02, 2053	Mar. 02, 2053
Fixed Rate of 4.72%, Balloon due February 13, 2024 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.72%	4.72%
Periodic payments of interest and principal, expiry date	Feb. 13, 2024	Feb. 13, 2024
Fixed Rate of 4.58%, Balloon Due February 27, 2024 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.58%	4.58%
Periodic payments of interest and principal, expiry date	Feb. 27, 2024	Feb. 27, 2024
Fixed Rate of 4.31%, Balloon Due June 24, 2025 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.31%	4.31%
Periodic payments of interest and principal, expiry date	Jun. 24, 2025	Jun. 24, 2025
Fixed Rate of 4.85%, Balloon due February 13, 2026 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.85%	4.85%
Periodic payments of interest and principal, expiry date	Feb. 13, 2026	Feb. 13, 2026
Fixed Rate of 4.73%, Balloon Due February 27, 2026 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.73%	4.73%
Periodic payments of interest and principal, expiry date	Feb. 27, 2026	Feb. 27, 2026
Fixed Rate of 4.40%, Balloon Due June 2, 2026 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.40%	4.40%
Periodic payments of interest and principal, expiry date	Jun. 02, 2026	Jun. 02, 2026
Fixed Rate of 4.36%, Balloon Due June 24, 2026 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.36%	4.36%
Periodic payments of interest and principal, expiry date	Jun. 24, 2026	Jun. 24, 2026
Fixed Rate of 3.75%, Balloon Due January 30, 2027 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	3.75%	3.75%
Periodic payments of interest and principal, expiry date	Jan. 30, 2027	Jan. 30, 2027
Fixed Rate of 4.09%, Balloon Due June 27, 2027 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.09%	4.09%
Periodic payments of interest and principal, expiry date	Jun. 27, 2027	Jun. 27, 2027
Fixed Rate of 4.09%, Balloon Due August 2, 2027 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.09%	4.09%
Periodic payments of interest and principal, expiry date	Aug. 02, 2027	Aug. 02, 2027
Fixed Rate of 4.14%, Balloon Due August 4, 2027 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.14%	4.14%
Periodic payments of interest and principal, expiry date	Aug. 04, 2027	Aug. 04, 2027
Fixed Rate of 3.46%, Balloon Due December 1, 2027 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	3.46%	3.46%
Periodic payments of interest and principal, expiry date	Dec. 01, 2027	Dec. 01, 2027
Fixed Rate of 4.55%, Balloon Due June 2, 2028 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.55%	4.55%
Periodic payments of interest and principal, expiry date	Jun. 02, 2028	Jun. 02, 2028
Fixed Rate of 4.34%, Balloon due June 13, 2028 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.34%	4.34%
Periodic payments of interest and principal, expiry date	Jun. 13, 2028	Jun. 13, 2028
Fixed Rate of 5.04%, Balloon due February 13, 2029 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	5.04%	5.04%
Periodic payments of interest and principal, expiry date	Feb. 13, 2029	Feb. 13, 2029
Fixed Rate of 4.98%, Balloon Due February 27, 2029 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.98%	4.98%
Periodic payments of interest and principal, expiry date	Feb. 27, 2029	Feb. 27, 2029
Fixed Rate of 4.19%, Balloon Due June 27, 2029 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.19%	4.19%
Periodic payments of interest and principal, expiry date	Jun. 27, 2029	Jun. 27, 2029
Fixed Rate of 4.19%, Balloon Due August 2, 2029 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.19%	4.19%
Periodic payments of interest and principal, expiry date	Aug. 02, 2029	Aug. 02, 2029
Fixed Rate of 3.48%, Balloon Due December 2, 2029 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	3.48%	3.48%
Periodic payments of interest and principal, expiry date	Dec. 02, 2029	Dec. 02, 2029
Fixed Rate of 3.99%, Balloon Due January 30, 2030 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	3.99%	3.99%
Periodic payments of interest and principal, expiry date	Jan. 30, 2030	Jan. 30, 2030
Fixed Rate of 4.44%, Balloon Due June 13, 2030 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.44%	4.44%
Periodic payments of interest and principal, expiry date	Jun. 13, 2030	Jun. 13, 2030
Fixed Rate of 5.14%, Balloon due March 13, 2031 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	5.14%	5.14%
Periodic payments of interest and principal, expiry date	Mar. 13, 2031	Mar. 13, 2031
Fixed Rate of 4.70%, Balloon Due June 2, 2031 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.70%	4.70%
Periodic payments of interest and principal, expiry date	Jun. 02, 2031	Jun. 02, 2031
Fixed Rate of 4.09%, Balloon Due January 30, 2032 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.09%	4.09%
Periodic payments of interest and principal, expiry date	Jan. 30, 2032	Jan. 30, 2032
Fixed Rate of 4.34%, Balloon Due June 27, 2032 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.34%	4.34%
Periodic payments of interest and principal, expiry date	Jun. 27, 2032	Jun. 27, 2032
Fixed Rate of 4.34%, Balloon Due August 2, 2032 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.34%	4.34%
Periodic payments of interest and principal, expiry date	Aug. 02, 2032	Aug. 02, 2032
Fixed Rate of 4.59%, Balloon due June 13, 2033 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.59%	4.59%
Periodic payments of interest and principal, expiry date	Jun. 13, 2033	Jun. 13, 2033
Fixed Rate of 5.29%, balloon due March 13, 2034 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	5.29%	5.29%
Periodic payments of interest and principal, expiry date	Mar. 13, 2034	Mar. 13, 2034
Fixed Rate of 4.48%, Balloon Due June 12, 2034 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.48%	4.48%
Periodic payments of interest and principal, expiry date	Jun. 12, 2034	Jun. 12, 2034
Fixed Rate of 4.24%, Balloon Due January 30, 2035 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.24%	4.24%
Periodic payments of interest and principal, expiry date	Jan. 30, 2035	Jan. 30, 2035
Fixed Rate of 2.44%, Balloon Due February 10, 2036 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	2.44%	2.44%
Periodic payments of interest and principal, expiry date	Feb. 10, 2036	Feb. 10, 2036
Fixed Rate of 2.46%, Balloon Due May 5, 2036 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	2.46%	2.46%
Periodic payments of interest and principal, expiry date	May 05, 2036	May 05, 2036
Fixed Rate of 4.69%, Balloon Due June 13, 2038 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.69%	4.69%
Periodic payments of interest and principal, expiry date	Jun. 13, 2038	Jun. 13, 2038
Fixed Rate of 5.45%, balloon due March 13, 2039 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	5.45%	5.45%
Periodic payments of interest and principal, expiry date	Mar. 13, 2039	Mar. 13, 2039
Fixed Rate of 4.49%, Balloon Due January 30, 2040 [Member]
Debt Instrument [Line Items]
Periodic payment of interest	4.49%	4.49%
Periodic payments of interest and principal, expiry date	Jan. 30, 2040	Jan. 30, 2040
Prime or SOFR Plus up to 1.075%, Expires June 22, 2028 [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Periodic payment of interest	1.075%	1.075%
Periodic payments of interest and principal, expiry date	Jun. 22, 2028	Jun. 22, 2028
Facility B [Member] | Interbank rates plus 1.500% Expires October 31, 2025 [Member] | Premium Financing Debt Facility [Member] | AUD Denominated Tranche [Member]
Debt Instrument [Line Items]
Periodic payment of interest	1.50%	1.50%
Facility B [Member] | Interbank Rates Plus 1.850% Expires October 31, 2025 [Member] | Premium Financing Debt Facility [Member] | NZD Denominated Tranche [Member]
Debt Instrument [Line Items]
Periodic payment of interest	1.85%	1.85%
Facility C and D [Member] | Interbank Rates Plus 0.830% Expires October 31, 2025 [Member] | Premium Financing Debt Facility [Member] | AUD Denominated Tranche [Member]
Debt Instrument [Line Items]
Periodic payment of interest	0.83%	0.83%
Facility C and D [Member] | Interbank Rates Plus 0.990% Expires October 31, 2025 [Member] | Premium Financing Debt Facility [Member] | NZD Denominated Tranche [Member]
Debt Instrument [Line Items]
Periodic payment of interest	0.99%	0.99%

Credit and Other Debt Agreeme_5

Credit and Other Debt Agreements - Additional Information (Detail) - USD ($) $ in Millions	Feb. 12, 2024	Jun. 30, 2024	Dec. 31, 2023
Fixed Rate of 5.45%, Balloon Due July 15, 2034 [Member]
Debt Instrument [Line Items]
Periodic payment of interest		5.45%	5.45%
Fixed Rate of 5.75%, Balloon Due July 15, 2054 [Member]
Debt Instrument [Line Items]
Periodic payment of interest		5.75%	5.75%
Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Notes issued and sold	$ 1,000
Weighted average interest rate	5.71%
Realized a cash gain (loss) on hedging transaction	$ 1.4
Derivative instrument, term	10 years
Unsecured Senior Notes [Member] | Fixed Rate of 5.45%, Balloon Due July 15, 2034 [Member]
Debt Instrument [Line Items]
Notes issued and sold	$ 500
Periodic payment of interest	5.45%
Periodic payments of interest and principal, expiry year	2034
Unsecured Senior Notes [Member] | Fixed Rate of 5.75%, Balloon Due July 15, 2054 [Member]
Debt Instrument [Line Items]
Notes issued and sold	$ 500
Periodic payment of interest	5.75%
Periodic payments of interest and principal, expiry year	2054

Earnings Per Share - Computatio

Earnings Per Share - Computation of Basic and Diluted Net EPS (Detail) - 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 earnings attributable to controlling interests	$ 283.4	$ 234.5	$ 891.8	$ 721
Weighted average number of common shares outstanding	218.8	214.9	218.1	213.8
Dilutive effect of stock options using the treasury stock method	4.1	4.1	4.3	4.2
Weighted average number of common and common equivalent shares outstanding	222.9	219	222.4	218
Basic net earnings per share	$ 1.3	$ 1.09	$ 4.09	$ 3.37
Diluted net earnings per share	$ 1.27	$ 1.07	$ 4.01	$ 3.31

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Earnings Per Share [Abstract]
Anti-dilutive stock-based awards shares outstanding	1	1.1	0.7	0.7

Stock Option Plans - Additional

Stock Option Plans - Additional information (Detail) - USD ($) $ / shares in Units, $ in Millions				3 Months Ended				6 Months Ended
	Mar. 01, 2024	Mar. 15, 2023	May 10, 2022	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Stock Option Plans [Line Items]
Compensation expense related to stock option grants				$ 10.5	$ 15.1	$ 7.8	$ 7.7	$ 25.6	$ 15.5
Total intrinsic value of options exercised								173.7	$ 123.8
Total unrecognized compensation cost related to nonvested options				$ 149.9				$ 149.9
Weighted average period, years								4 years
Black-Scholes Option Pricing Model [Member]
Stock Option Plans [Line Items]
Weighted average fair value per option for all options								$ 69.55	$ 46.48
Long Term Incentive Plan [Member]
Stock Option Plans [Line Items]
Stock option granted, Share pool			13,500,000
Shares against the pool			3.8
Maximum number of shares available			3,500,000					2,500,000
Number Of Periods Options Expire								7 years
Shares available for grant				10,900,000				10,900,000
Long Term Incentive Plan [Member] | Officer and Key Employees [Member]
Stock Option Plans [Line Items]
Shares available for grant	1,044,000	1,131,000
Stock options granted, exercise percentage, on the third anniversary date of the grant	34%	34%
Stock options granted, exercise percentage, on the fourth anniversary date of the grant	33%	33%
Stock options granted, exercise percentage, on the fifth anniversary date of the grant	33%	33%
Long Term Incentive Plan [Member] | Maximum [Member]
Stock Option Plans [Line Items]
Minimum exercise price of stock options, percent of fair market value of a share of common stock on the date of grant								100%
Maximum period for the exercise of stock options, years								7 years	7 years
Long Term Incentive Plan [Member] | Minimum [Member]
Stock Option Plans [Line Items]
Period of service from grant date stock options awarded not subject to forfeiture		2 years							2 years
Long Term Incentive Plan [Member] | Minimum [Member] | Executive Officer [Member]
Stock Option Plans [Line Items]
Minimum age of employee with not subject to award forfeiture on condition compliance								62 years	55 years

Stock Option Plans - Black-Scho

Stock Option Plans - Black-Scholes Option Pricing Model with Weighted Average (Detail)	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Expected dividend yield	1%	1.20%
Expected risk-free interest rate	4.20%	3.60%
Volatility	25.30%	25%
Expected life (in years)	5 years 6 months	5 years 4 months 24 days

Stock Option Plans - Stock Opti

Stock Option Plans - Stock Option Activity and Related Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2024
Share-Based Payment Arrangement [Abstract]
Shares Under Option, Beginning balance	7.9
Shares Under Option, Granted	1
Shares Under Option, Exercised	(1)
Shares Under Option, Forfeited or canceled	(0.1)
Shares Under Option, Ending balance	7.8
Shares Under Option, Exercisable at end of period	2.1
Shares Under Option, Ending unvested and expected to vest	5.2
Weighted Average Exercise Price, Beginning balance	$ 123.85
Weighted Average Exercise Price, Granted	243.54
Weighted Average Exercise Price, Exercised	76.4
Weighted Average Exercise Price, Forfeited or canceled	151.05
Weighted Average Exercise Price, Ending balance	145.7
Weighted Average Exercise Price, Exercisable at end of period	88.79
Weighted Average Exercise Price, Ending unvested and expected to vest	$ 164.5
Weighted Average Remaining Contractual Term (in years), Ending balance	4 years 2 months 4 days
Weighted Average Remaining Contractual Term (in years), Exercisable at end of year	2 years 2 months 8 days
Weighted Average Remaining Contractual Term (in years), Ending unvested and expected to vest	4 years 10 months 9 days
Aggregate Intrinsic Value, Ending Balance	$ 883.9
Aggregate Intrinsic Value, Exercisable at end of year	353.9
Aggregate Intrinsic Value, Ending unvested and expected to vest	$ 494.1

Stock Option Plans - Stock Op_2

Stock Option Plans - Stock Options Outstanding and Exercisable (Detail) - $ / shares shares in Millions	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 70.74
Range of Exercise Prices, maximum	$ 243.54
Option Outstanding, Number Outstanding	7.8
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	4 years 2 months 4 days
Option Outstanding, Weighted Average Exercise Price	$ 145.7	$ 123.85
Options Exercisable, Number Exercisable	2.1
Option Exercisable, Weighted Average Exercise Price	$ 88.79
Exercise Prices Range $ 70.74 - $ 70.74 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	70.74
Range of Exercise Prices, maximum	$ 70.74
Option Outstanding, Number Outstanding	0.4
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	8 months 15 days
Option Outstanding, Weighted Average Exercise Price	$ 70.74
Options Exercisable, Number Exercisable	0.4
Option Exercisable, Weighted Average Exercise Price	$ 70.74
Exercise Prices Range $ 79.59 - $ 79.59 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	79.59
Range of Exercise Prices, maximum	$ 79.59
Option Outstanding, Number Outstanding	0.7
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	1 year 8 months 12 days
Option Outstanding, Weighted Average Exercise Price	$ 79.59
Options Exercisable, Number Exercisable	0.7
Option Exercisable, Weighted Average Exercise Price	$ 79.59
Exercise Prices Range $ 86.17 - $ 86.17 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	86.17
Range of Exercise Prices, maximum	$ 86.17
Option Outstanding, Number Outstanding	1.1
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	2 years 8 months 12 days
Option Outstanding, Weighted Average Exercise Price	$ 86.17
Options Exercisable, Number Exercisable	0.6
Option Exercisable, Weighted Average Exercise Price	$ 86.17
Exercise Prices Range $ 127.90 - $ 127.90 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	127.9
Range of Exercise Prices, maximum	$ 127.9
Option Outstanding, Number Outstanding	1.4
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	3 years 8 months 15 days
Option Outstanding, Weighted Average Exercise Price	$ 127.9
Options Exercisable, Number Exercisable	0.4
Option Exercisable, Weighted Average Exercise Price	$ 127.9
Exercise Prices Range $ 156.85 - $ 156.85 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	156.85
Range of Exercise Prices, maximum	$ 156.85
Option Outstanding, Number Outstanding	1
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	4 years 7 months 2 days
Option Outstanding, Weighted Average Exercise Price	$ 156.85
Exercise Prices Range $ 158.56 - $ 161.14 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	158.56
Range of Exercise Prices, maximum	$ 161.14
Option Outstanding, Number Outstanding	1.1
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	4 years 8 months 19 days
Option Outstanding, Weighted Average Exercise Price	$ 158.65
Exercise Prices Range $ 177.09 - $ 202.13 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	177.09
Range of Exercise Prices, maximum	$ 202.13
Option Outstanding, Number Outstanding	1.1
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	5 years 8 months 19 days
Option Outstanding, Weighted Average Exercise Price	$ 177.78
Exercise Prices Range $ 238.88 - $ 243.54 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	238.88
Range of Exercise Prices, maximum	$ 243.54
Option Outstanding, Number Outstanding	1
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	6 years 8 months 1 day
Option Outstanding, Weighted Average Exercise Price	$ 243.54

Deferred Compensation - Additio

Deferred Compensation - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Investments And Employee Deferred Compensation Plan [Line Items]
Deferred Equity Participation Plan, distributions to key executives, age					age 62 (or the one-year anniversary of the date of the grant for participants over the age of 61 as of the grant date) or upon or after their actual retirement if later.
Deferred Equity Participation Sub-plans, distributions requisite service description					we annually make awards under sub-plans of the DEPP for certain production staff, which generally provide for vesting and/or distributions no sooner than five years from the date of awards, although certain awards vest and/or distribute after the earlier of fifteen years or the participant reaching age 65.
Deferred Equity Participation Sub-plans, distributions to key executives, age					age 65
Deferred Equity Participation Plan (DEPP) [Member]
Investments And Employee Deferred Compensation Plan [Line Items]
Awards approved by committee, value		$ 23.2		$ 25.1
Charge to compensation expenses related to awards	$ 5.6		$ 5.9		$ 9.6	$ 9.9
Unearned deferred compensation, value					$ 95.5		$ 81.1
Unearned deferred compensation, shares					2.3		2.2
Total intrinsic value of unvested equity based awards					$ 584.4		$ 504.9
Cash and equity awards with aggregate fair value vested and distributed to participants					17.9	9.4
Deferred Equity Participation Plan Sub Plans [Member]
Investments And Employee Deferred Compensation Plan [Line Items]
Awards approved by committee, value		2.3		3
Charge to compensation expenses related to awards	0.6		0.8		1.1	1.4
Distributions from the sub-plans					2.3	6.4
Deferred Cash Participation Plan (DCPP) [Member]
Investments And Employee Deferred Compensation Plan [Line Items]
Awards approved by committee, value		$ 8.1		$ 9.8
Charge to compensation expenses related to awards	$ 5.1		$ 4.2		9.9	8
Cash and equity awards with aggregate fair value vested and distributed to participants					$ 13.6	$ 19.5

Restricted Stock, Performance_2

Restricted Stock, Performance Share and Cash Awards - Additional Information (Detail) $ in Millions

3 Months Ended

6 Months Ended

Mar. 01, 2024 USD ($) shares

Mar. 15, 2023 USD ($) shares

May 10, 2022 shares

Jun. 30, 2024 USD ($) shares

Mar. 31, 2024 USD ($) shares

Jun. 30, 2023 USD ($) shares

Mar. 31, 2023 USD ($) shares

Jun. 30, 2024 USD ($) TIME shares

Jun. 30, 2023 USD ($) shares

Dec. 31, 2023 shares

Mar. 31, 2022 shares

Mar. 15, 2022 USD ($) shares

Mar. 16, 2021 USD ($) shares

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Share-based compensation, shares outstanding | shares

7,800,000

7,800,000

7,900,000

Officer and Key Employees [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Performance awards period, years

1 year

Restricted Stock Units (RSUs) [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Share based payment award vesting date

Mar. 01, 2029

Mar. 15, 2028

Restricted stock or unit expense

$ 14.1

$ 11

$ 27

$ 20.7

Unvested Restricted Stock [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Total intrinsic value

512.7

460.5

512.7

460.5

Equity awards with an aggregate fair value

93.3

62

Performance Shares [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Restricted stock or unit expense

5.6

3.8

10.6

8.5

Total intrinsic value

85.2

64.3

85.2

64.3

Equity awards with an aggregate fair value

$ 31.6

$ 28.9

Performance share awards approved, Fair value

$ 14.2

$ 10.3

Vesting period, years

3 years

3 years

Performance Shares [Member] | Executive Officer [Member] | Minimum [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Minimum age of employee with not subject to award forfeiture on condition compliance

62 years

62 years

2017 Performance Share Awards [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Provisional awards, terms

The 2024 and 2023 awards are subject to a three-year performance period that began on January 1, 2024 and 2023, respectively, and vest on the three-year anniversary of the date of grant (March 1, 2027 and March 15, 2026).

Cash Awards [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Shares granted in the period | shares

0

0

Cash Awards [Member] | Officer and Key Employees [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Provisional awards, terms

The ultimate award value will be equal to the trailing twelve-month price of our common stock, multiplied by the number of units subject to the award, but limited to between 0.5 and 1.5 times the original value of the units determined as of the grant date.

Vesting period, years

3 years

Provisional compensation cash awards approved for future grant by compensation committee, value

$ 19.9

$ 18.8

Provisional compensation cash award approved for future grant by compensation committee, units | shares

125,000

147,000

Ultimate award value, multiples of original value of the units, minimum | TIME

0.5

Ultimate award value, multiples of original value of the units, maximum | TIME

1.5

2022 Provisional Cash Awards [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Cash-based compensation awards, expenses

$ 3.3

3.1

$ 6.7

$ 5.7

2021 Provisional Cash Awards [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Provisional compensation cash award approved for future grant by compensation committee, units | shares

129,000

129,000

Cash-based compensation awards, expenses

$ 3.2

$ 6.5

Cash award with aggregate fair value vested and distributed to participants

$ 25.4

Performance awards expiration date

Jan. 01, 2024

2021 Provisional Cash Awards [Member] | Officer and Key Employees [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Provisional compensation cash award approved for future grant by compensation committee, units | shares

143,000

2020 Provisional Cash Awards [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Provisional compensation cash award approved for future grant by compensation committee, units | shares

191,000

191,000

Cash award with aggregate fair value vested and distributed to participants

$ 24.7

Long Term Incentive Plan [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Share-based compensation, shares outstanding, Value

$ 4

$ 4

Shares granted in the period | shares

3,500,000

2,500,000

Long Term Incentive Plan [Member] | Minimum [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Period of service from grant date stock options awarded not subject to forfeiture

2 years

2 years

Long Term Incentive Plan [Member] | Executive Officer [Member] | Minimum [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Minimum age of employee with not subject to award forfeiture on condition compliance

62 years

55 years

Long Term Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Shares granted in the period | shares

345,000

378,000

Fair value of grants in period

$ 83.9

$ 67

Long Term Incentive Plan [Member] | Performance Shares [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Shares authorized | shares

58,000

58,000

Long Term Incentive Plan [Member] | Performance Shares [Member] | Executive Officer [Member] | Minimum [Member]

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Minimum age of employee with not subject to award forfeiture on condition compliance

55 years

Derivatives and Hedging Activ_3

Derivatives and Hedging Activity - Summary of Notional and Fair Values of Derivative Instruments (Detail) - USD ($)		Jun. 30, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Notional Amount		$ 46,400,000	$ 217,800,000
Derivative Assets		15,000,000	18,100,000
Derivative Liabilities		6,700,000	13,600,000
Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Notional Amount			150,000,000
Interest Rate Contracts [Member] | Accrued compensation and other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities			5,700,000
Foreign Exchange Contracts [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	[1]	46,400,000	67,800,000
Foreign Exchange Contracts [Member] | Other current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	[1]	4,900,000	3,900,000
Foreign Exchange Contracts [Member] | Other noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets		10,100,000	14,200,000
Foreign Exchange Contracts [Member] | Accrued compensation and other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	[1]	2,600,000	3,900,000
Foreign Exchange Contracts [Member] | Other noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities		$ 4,100,000	$ 4,000,000
[1] Included within foreign exchange contracts at June 30, 2024 were $ 819.3 million of call options, offset with $ 819.3 million of put options, and $ 3.0 million of buy forwards, offset with $ 49.4 million of sell forwards. Included within foreign exchange contracts at December 31, 2023 were $ 331.3 million of call options, offset with $ 331.3 million of put options, and $ 5.5 million of buy forwards, offset with $ 73.3 million of sell forwards.

Derivatives and Hedging Activ_4

Derivatives and Hedging Activity - Summary of Notional and Fair Values of Derivative Instruments (Parenthetical) (Detail) - Foreign Exchange Contracts [Member] - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Call Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	$ 819.3	$ 331.3
Put Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	819.3	331.3
Forward Contracts [Member] | Call Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	49.4	73.3
Forward Contracts [Member] | Put Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	$ 3	$ 5.5

Derivatives and Hedging Activ_5

Derivatives and Hedging Activity - Summary of Amounts of Derivative Gains (Losses) Recognized In Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss	[1]	$ (4)	$ 31.7	$ (6.7)	$ 37.5
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Earnings		(2.1)	(1)	(3)	(1.5)
Amount of Gain Recognized in Earnings Related to Amount Excluded from Effectiveness Testing		0.4	0.7	0.9	1.7
Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Earnings		$ (0.3)	$ (0.3)	$ (0.6)	$ (0.6)
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration]		Interest Expense, Operating and Nonoperating	Interest Expense, Operating and Nonoperating	Interest Expense, Operating and Nonoperating	Interest Expense, Operating and Nonoperating
Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Earnings		$ (1)	$ 0.2	$ (0.8)	$ 0.8
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration]		Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax
Interest expense [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss	[1]	$ (3.6)	$ 18.9	$ (2.9)	$ 8.8
Commission revenue [Member] | Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss	[1]	(0.4)	12.8	(3.8)	28.7
Compensation expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Earnings		(0.4)	(0.5)	(0.9)	(1)
Amount of Gain Recognized in Earnings Related to Amount Excluded from Effectiveness Testing		$ 0.2	$ 0.4	$ 0.5	$ 1
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration]		Labor and Related Expense	Labor and Related Expense	Labor and Related Expense	Labor and Related Expense
Operating expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Earnings		$ (0.4)	$ (0.4)	$ (0.7)	$ (0.7)
Amount of Gain Recognized in Earnings Related to Amount Excluded from Effectiveness Testing		$ 0.2	$ 0.3	$ 0.4	$ 0.7
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration]		Operating Expenses	Operating Expenses	Operating Expenses	Operating Expenses
[1] For the three and six-month periods ended June 30, 2024 , the amount excluded from the assessment of hedge effectiveness for our foreign exchange contracts recognized in accumulated other comprehensive loss was a loss of $ 0.1 million and a gain of $ 0.2 million, respectively. For the three and six-month periods ended June 30, 2023 , the amount excluded from the assessment of hedge effectiveness for our foreign exchange contracts recognized in accumulated other comprehensive loss was a gain of $ 0.3 million and $ 0.8 million, respectively.

Derivatives and Hedging Activ_6

Derivatives and Hedging Activity - Summary of Amounts of Derivative Gains (Losses) Recognized In Accumulated Other Comprehensive Loss (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive income (loss), foreign currency transaction and translation adjustment, net of tax	$ 11.4	$ (155.8)	$ 193.8	$ 33.2
Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive income (loss), foreign currency transaction and translation adjustment, net of tax	$ (0.1)		$ 0.3		$ 0.2	$ 0.8

Derivatives and Hedging Activ_7

Derivatives and Hedging Activity - Additional Information (Detail) $ in Millions	12 Months Ended
	Jun. 30, 2025 USD ($)
Scenario, Forecast [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Estimated pretax gain to be reclassified from accumulated other comprehensive loss into earnings	$ 13

Commitments, Contingencies an_3

Commitments, Contingencies and Off-Balance Sheet Arrangements - Contractual Obligations (Detail) $ in Millions	Jun. 30, 2024 USD ($)
Senior Notes [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, Thereafter	$ 4,550
Contractual Obligations, Payments Due by Period, Total	4,550
Note Purchase Agreements [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2025	200
Contractual Obligations, Payments Due by Period, 2026	640
Contractual Obligations, Payments Due by Period, 2027	478
Contractual Obligations, Payments Due by Period, 2028	200
Contractual Obligations, Payments Due by Period, Thereafter	2,005
Contractual Obligations, Payments Due by Period, Total	3,523
Credit Agreement [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2024	80
Contractual Obligations, Payments Due by Period, Total	80
Premium Financing Debt Facility [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2024	207.8
Contractual Obligations, Payments Due by Period, Total	207.8
Interest On Debt [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2024	184.4
Contractual Obligations, Payments Due by Period, 2025	374
Contractual Obligations, Payments Due by Period, 2026	355
Contractual Obligations, Payments Due by Period, 2027	336.7
Contractual Obligations, Payments Due by Period, 2028	317.2
Contractual Obligations, Payments Due by Period, Thereafter	4,285.8
Contractual Obligations, Payments Due by Period, Total	5,853.1
Total Debt Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2024	472.2
Contractual Obligations, Payments Due by Period, 2025	574
Contractual Obligations, Payments Due by Period, 2026	995
Contractual Obligations, Payments Due by Period, 2027	814.7
Contractual Obligations, Payments Due by Period, 2028	517.2
Contractual Obligations, Payments Due by Period, Thereafter	10,840.8
Contractual Obligations, Payments Due by Period, Total	14,213.9
Operating Lease Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2024	54.2
Contractual Obligations, Payments Due by Period, 2025	108.9
Contractual Obligations, Payments Due by Period, 2026	90.5
Contractual Obligations, Payments Due by Period, 2027	73.3
Contractual Obligations, Payments Due by Period, 2028	55.8
Contractual Obligations, Payments Due by Period, Thereafter	92.4
Contractual Obligations, Payments Due by Period, Total	475.1
Less Sublease Arrangements [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Receivable by Period, 2024	(1.2)
Contractual Obligations, Payments Receivable by Period, 2025	(1.8)
Contractual Obligations, Payments Receivable by Period, 2026	(1.7)
Contractual Obligations, Payments Receivable by Period, 2027	(1.6)
Contractual Obligations, Payments Receivable by Period, 2028	(1.1)
Contractual Obligations, Payments Receivable by Period, Thereafter	(0.8)
Contractual Obligations, Payments Receivable by Period, Total	(8.2)
Outstanding Purchase Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2024	80
Contractual Obligations, Payments Due by Period, 2025	71.6
Contractual Obligations, Payments Due by Period, 2026	29
Contractual Obligations, Payments Due by Period, 2027	23.3
Contractual Obligations, Payments Due by Period, 2028	16.9
Contractual Obligations, Payments Due by Period, Thereafter	48.3
Contractual Obligations, Payments Due by Period, Total	269.1
Total Contractual Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2024	605.2
Contractual Obligations, Payments Due by Period, 2025	752.7
Contractual Obligations, Payments Due by Period, 2026	1,112.8
Contractual Obligations, Payments Due by Period, 2027	909.7
Contractual Obligations, Payments Due by Period, 2028	588.8
Contractual Obligations, Payments Due by Period, Thereafter	10,980.7
Contractual Obligations, Payments Due by Period, Total	$ 14,949.9

Commitments, Contingencies an_4

Commitments, Contingencies and Off-Balance Sheet Arrangements - Additional Information (Detail)	3 Months Ended		6 Months Ended		270 Months Ended
	Jun. 30, 2024 USD ($) ft² Entity LetterOfCredit	Jun. 30, 2023 Entity	Jun. 30, 2024 USD ($) ft² LetterOfCredit Entity	Jun. 30, 2023 Entity	Jun. 30, 2024 USD ($) ft² Entity LetterOfCredit
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of square feet | ft²	360,000		360,000		360,000
Number of companies acquired | Entity	30	34	58	45	725
Aggregate amount of maximum earnout obligations related to acquisitions			$ 1,925,800,000
Aggregate amount of maximum earnout obligations related to acquisitions, recorded in consolidated balance sheet			1,236,700,000
Aggregate amount of earnout obligation expected settlement in cash or stock at option	$ 491,800,000		491,800,000		$ 491,800,000
Aggregate amount of earnout obligation expected settlement in cash	$ 744,900,000		744,900,000		$ 744,900,000
Income tax credits and adjustments			$ 108,000,000
Collateral [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of letters of credit issued | LetterOfCredit	1		1		1
Security Deposit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of letters of credit issued | LetterOfCredit	1		1		1
Self-Insurance Deductibles [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of letters of credit issued | LetterOfCredit	2		2		2
Rent-A-Captive Facility [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of letters of credit issued | LetterOfCredit	8		8		8
Errors And Omissions [Member] | Up to $4.5 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claims, amount retained			$ 2,000,000
Errors And Omissions [Member] | Up to $10 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claims, amount retained			15,000,000
Errors And Omissions [Member] | Up to $20.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claims, amount retained			10,000,000
Errors And Omissions [Member] | Up to $27.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claims, amount retained			20,000,000
Letter of Credit [Member] | Collateral [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Debt	$ 500,000		500,000		$ 500,000
Letter of Credit [Member] | Security Deposit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Debt	900,000		900,000		900,000
Letter of Credit [Member] | Self-Insurance Deductibles [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Debt	9,300,000		9,300,000		9,300,000
Liabilities recorded on self-insurance	14,000,000		14,000,000		14,000,000
Letter of Credit [Member] | Rent-A-Captive Facility [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Debt	13,000,000		13,000,000		13,000,000
Minimum [Member] | Errors And Omissions [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Loss Contingency Accrual, Product Liability, Net, Total	8,800,000		8,800,000		8,800,000
Minimum [Member] | Errors And Omissions [Member] | Up to $4.5 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	15,000,000		15,000,000		15,000,000
Minimum [Member] | Errors And Omissions [Member] | Up to $20.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	100,000,000		100,000,000		100,000,000
Minimum [Member] | Errors And Omissions [Member] | Up to $27.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	225,000,000		225,000,000		225,000,000
Maximum [Member] | Errors And Omissions [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Loss Contingency Accrual, Product Liability, Net, Total	6,200,000		6,200,000		6,200,000
Maximum [Member] | Errors And Omissions [Member] | Up to $4.5 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	100,000,000		100,000,000		100,000,000
Maximum [Member] | Errors And Omissions [Member] | Up to $20.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	225,000,000		225,000,000		225,000,000
Maximum [Member] | Errors And Omissions [Member] | Up to $27.0 Million [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claim arise during ordinary course of business	$ 400,000,000		$ 400,000,000		$ 400,000,000
Unconsolidated Investments in Enterprises [Member] | Minimum [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Ownership interest	1%		1%		1%
Unconsolidated Investments in Enterprises [Member] | Maximum [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Ownership interest	50%		50%		50%

Commitments, Contingencies an_5

Commitments, Contingencies and Off-Balance Sheet Arrangements - Off-Balance Sheet Commitments (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2024 USD ($)
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Amount of Commitment Expiration by Period - 2024	$ 1
Amount of Commitment Expiration by Period - Thereafter	23.7
Total Amounts Committed	24.7
Financial Guarantees [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Amount of Commitment Expiration by Period - 2024	1
Total Amounts Committed	1
Letters of Credit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Amount of Commitment Expiration by Period - Thereafter	23.7
Total Amounts Committed	$ 23.7

Supplemental Disclosures of C_3

Supplemental Disclosures of Cash Flow Information - Cash Flow (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash and Cash Equivalents [Abstract]
Interest paid	$ 162.1	$ 127.3
Income taxes paid, net	$ 167.8	$ 116.7

Supplemental Disclosures of C_4

Supplemental Disclosures of Cash Flow Information - Cash Equivalents, Restricted Cash and Fiduciary Cash (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents - non-restricted cash	$ 1,219.2		$ 777.9
Cash and cash equivalents - restricted cash	196.1		174.4
Total cash and cash equivalents	1,415.3	$ 971.5	952.3
Fiduciary cash	5,422.5	$ 5,571.8	5,989.9
Total cash, cash equivalents, restricted cash and fiduciary cash	$ 6,837.8		$ 6,942.2

Supplemental Disclosures of C_5

Supplemental Disclosures of Cash Flow Information - Additional Information (Detail) - Qualified Contributory Savings and Thrift 401(k) Plan [Member] - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Matching contributions by employer, percentage	100%
Percentage of eligible compensation for matching contributions by employer	5%	5%
Matching contributions vesting schedule	5 years
Contribution expense to plan	$ 56	$ 42.3
Employer match on eligible compensation			5%	5%

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss Attributable to Controlling Interests (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2024 USD ($)
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ (792.1)
Ending Balance	(939.2)
Pension Liability [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(37.1)
Net change in period	0.2
Ending Balance	(36.9)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(867.4)
Net change in period	(144.5)
Ending Balance	(1,011.9)
Fair Value of Derivative Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	112.4
Net change in period	(2.8)
Ending Balance	109.6
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(792.1)
Net change in period	(147.1)
Ending Balance	$ (939.2)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Loss - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Expense related to pension liability reclassified from accumulated other comprehensive earnings	$ 1,000,000	$ 2,600,000
Income (expense) related to fair value of derivative investments reclassified from accumulated other comprehensive earnings	(3,000,000)	(1,500,000)
Foreign currency translation reclassified from accumulated other comprehensive earnings	$ 0	$ 0

Segment Information - Additiona

Segment Information - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2024 Segment
Segment Reporting [Abstract]
Number of reportable segments	3

Segment Information - Schedule

Segment Information - Schedule of Segment Reporting Information by Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Total revenues	$ 2,775.4	$ 2,441.9	$ 6,032.1	$ 5,148
Earnings before income taxes	365.6	297.4	1,138.3	903.2
Identifiable assets at June 30, 2024 and 2023	63,007.7	54,365.2	63,007.7	54,365.2	$ 51,615.8
Operating Segments [Member] | Brokerage [Member]
Segment Reporting Information [Line Items]
Total revenues	2,376.3	2,088.4	5,241.2	4,463.6
Earnings before income taxes	446.3	390.5	1,322.4	1,081.4
Identifiable assets at June 30, 2024 and 2023	58,776.7	50,623.8	58,776.7	50,623.8
Operating Segments [Member] | Risk Management [Member]
Segment Reporting Information [Line Items]
Total revenues	398	353.6	789.4	684.4
Earnings before income taxes	65.4	49.9	118.6	95.4
Identifiable assets at June 30, 2024 and 2023	1,683.4	1,212.8	1,683.4	1,212.8
Operating Segments [Member] | Corporate [Member]
Segment Reporting Information [Line Items]
Total revenues	1.1	(0.1)	1.5
Earnings before income taxes	(146.1)	(143)	(302.7)	(273.6)
Identifiable assets at June 30, 2024 and 2023	$ 2,547.6	$ 2,528.6	$ 2,547.6	$ 2,528.6

Segment Information - Summary o

Segment Information - Summary of Revenues by Type and Segment (Detail) - 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]
Revenues before reimbursements	$ 2,736	$ 2,406.9	$ 5,954.1	$ 5,079.8
Reimbursements	39.4	35	78	68.2
Total revenues	2,775.4	2,441.9	6,032.1	5,148
Unites States [Member]
Segment Reporting Information [Line Items]
Total revenues	1,719.9	1,498.3	3,854.8	3,253.8
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total revenues	588.6	539.2	1,187.4	1,064
Australia [Member]
Segment Reporting Information [Line Items]
Total revenues	146.9	121.3	267.9	219.5
Canada [Member]
Segment Reporting Information [Line Items]
Total revenues	112	106.1	216.8	201.3
New Zealand [Member]
Segment Reporting Information [Line Items]
Total revenues	58	57.3	101.9	99.2
Other Foreign [Member]
Segment Reporting Information [Line Items]
Total revenues	150	119.7	403.3	310.2
Brokerage [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	2,376.3	2,088.4	5,241.2	4,463.6
Total revenues	2,376.3	2,088.4	5,241.2	4,463.6
Brokerage [Member] | Unites States [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1,394.6	1,199.7	3,208.6	2,675
Brokerage [Member] | United Kingdom [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	574.6	527.6	1,159.4	1,041.1
Brokerage [Member] | Australia [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	90.9	83.8	158.9	148
Brokerage [Member] | Canada [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	110.3	104.6	213.4	198.3
Brokerage [Member] | New Zealand [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	55.9	53	97.6	91
Brokerage [Member] | Other Foreign [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	150	119.7	403.3	310.2
Risk Management [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	358.6	318.6	711.4	616.2
Reimbursements	39.4	35	78	68.2
Total revenues	398	353.6	789.4	684.4
Risk Management [Member] | Unites States [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	324.2	298.7	644.7	578.8
Risk Management [Member] | United Kingdom [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	14	11.6	28	22.9
Risk Management [Member] | Australia [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	56	37.5	109	71.5
Risk Management [Member] | Canada [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1.7	1.5	3.4	3
Risk Management [Member] | New Zealand [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	2.1	4.3	4.3	8.2
Corporate [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	1.1	(0.1)	1.5
Total revenues	1.1	(0.1)	1.5
Corporate [Member] | Unites States [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1.1	(0.1)	1.5
Commissions [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	1,661.8	1,410.4	3,655.4	3,157.8
Commissions [Member] | Brokerage [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	1,661.8	1,410.4	3,655.4	3,157.8
Broker Fees [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	827.1	790.5	1,778.3	1,496.2
Broker Fees [Member] | Brokerage [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	477.6	478.5	1,084.3	891.2
Broker Fees [Member] | Risk Management [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	349.5	312	694	605
Supplemental Revenue Member [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	88.7	71.2	182.6	152.8
Supplemental Revenue Member [Member] | Brokerage [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	88.7	71.2	182.6	152.8
Contingent Revenue [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	59.8	54.2	145.8	126
Contingent Revenue [Member] | Brokerage [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	59.8	54.2	145.8	126
Interest Income Premium Finance Revenues and Other Income [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	98.6	80.6	192	147
Interest Income Premium Finance Revenues and Other Income [Member] | Brokerage [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	88.4	74.1	173.1	135.8
Interest Income Premium Finance Revenues and Other Income [Member] | Risk Management [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	9.1	6.6	17.4	11.2
Interest Income Premium Finance Revenues and Other Income [Member] | Corporate [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	1.1	(0.1)	1.5
Investment Income [Member]
Segment Reporting Information [Line Items]
Revenues before reimbursements	$ 98.6	$ 80.6	$ 192	$ 147

Segment Information - Summary_2

Segment Information - Summary of Geographical Location and Segment (Detail) - 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]
Total revenues	$ 2,775.4	$ 2,441.9	$ 6,032.1	$ 5,148
Unites States [Member]
Segment Reporting Information [Line Items]
Total revenues	1,719.9	1,498.3	3,854.8	3,253.8
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total revenues	588.6	539.2	1,187.4	1,064
Australia [Member]
Segment Reporting Information [Line Items]
Total revenues	146.9	121.3	267.9	219.5
Canada [Member]
Segment Reporting Information [Line Items]
Total revenues	112	106.1	216.8	201.3
New Zealand [Member]
Segment Reporting Information [Line Items]
Total revenues	58	57.3	101.9	99.2
Other Foreign [Member]
Segment Reporting Information [Line Items]
Total revenues	150	119.7	403.3	310.2
Brokerage [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	2,376.3	2,088.4	5,241.2	4,463.6
Brokerage [Member] | Unites States [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1,394.6	1,199.7	3,208.6	2,675
Brokerage [Member] | United Kingdom [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	574.6	527.6	1,159.4	1,041.1
Brokerage [Member] | Australia [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	90.9	83.8	158.9	148
Brokerage [Member] | Canada [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	110.3	104.6	213.4	198.3
Brokerage [Member] | New Zealand [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	55.9	53	97.6	91
Brokerage [Member] | Other Foreign [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	150	119.7	403.3	310.2
Risk Management [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	398	353.6	789.4	684.4
Risk Management [Member] | Unites States [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	324.2	298.7	644.7	578.8
Risk Management [Member] | United Kingdom [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	14	11.6	28	22.9
Risk Management [Member] | Australia [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	56	37.5	109	71.5
Risk Management [Member] | Canada [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1.7	1.5	3.4	3
Risk Management [Member] | New Zealand [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	2.1	4.3	4.3	$ 8.2
Corporate [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1.1	(0.1)	1.5
Corporate [Member] | Unites States [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	$ 1.1	$ (0.1)	$ 1.5