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- Definition

Business Acquisitions Purchase Price Allocation Goodwill Amount

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- Definition

Business acquisitionsnet earnings before interest, income taxes, depreciation, amortization and change in estimated acquisition earnout payables.

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- Definition

Business combination aggregate earnout obligation expected settlement in cash.

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Business combination aggregate earnout obligation expected settlement in cash or common stock at option.

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Business Combination ,Aggregate Earnout Obligation, Maximum

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Business Combination Aggregate Earnout Obligation Recorded Maximum

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Business Combination, Annualize Revenue

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Business combination, recognized identifiable assets acquired and liabilities assumed, intangible assets, expiration lists.

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Business combination, recognized identifiable assets acquired and liabilities assumed, intangible assets, non-compete agreements.

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Business combination, recognized identifiable assets acquired and liabilities assumed, intangible assets, trade names.

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Fair Value Inputs, Attrition Rate

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Number of employees.

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Amount after tax of pro forma income from continuing operations as if the business combination had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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For transactions that are recognized separately from the acquisition of assets and assumptions of liabilities in the business combination, such as related to pre-existing relationships with the acquiree, this element represents the disclosure of the amount of acquisition related costs which have been expensed.

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Amount of deferred tax liability attributable to taxable temporary differences.

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Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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The number of businesses acquired by the entity during the period.

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Business Combinations - Additional Information (Detail) $ in Millions					12 Months Ended
	Jan. 07, 2025 USD ($)	Dec. 19, 2024 USD ($)	Dec. 11, 2024 USD ($)	Dec. 07, 2024 USD ($)	Dec. 31, 2024 USD ($) Employee Entity	Dec. 31, 2023 USD ($) Entity	Dec. 31, 2022 USD ($) Entity
Business Acquisition [Line Items]
Cash raised through follow-on common stock offering					$ 8,506.8	$ 120.2	$ 123.1
Accretion of the discount on acquisition					61.7	76.6	61.0
Income (expense) related to net adjustments to estimated fair value of liability for earnout obligations					$ 35.7	$ (300.7)	$ (22.0)
Number of companies acquired \| Entity					91	80	89
Aggregate amount of maximum earnout obligations related to acquisitions					$ 1,998.2	$ 2,009.8
Aggregate amount of maximum earnout obligations related to acquisitions, recorded in consolidated balance sheet					1,302.0	1,294.2
Aggregate amount of earnout obligation expected settlement in cash or common stock at option					511.9	564.8
Aggregate amount of earnout obligation expected settlement in cash					790.1	729.4
Goodwill					837.2
Expiration lists					791.5
Non-compete agreements					23.6
Trade names					1.9
Write-off of amortizable intangible assets					19.4	3.5	$ 2.0
Total revenues					11,766.9	10,458.0
Goodwill					$ 12,270.2	11,475.6	9,489.4
Number of employees \| Employee					2,000
Brokerage Management [Member]
Business Acquisition [Line Items]
Goodwill					$ 837.2
Expiration lists					791.5
Non-compete agreements					23.6
Trade names					1.9
Brokerage [Member]
Business Acquisition [Line Items]
Goodwill					11,923.4	$ 11,217.8	$ 9,358.1
Brokerage [Member] \| Expiration Lists [Member]
Business Acquisition [Line Items]
Business acquisition not deductible for income tax purposes					239.8
Brokerage [Member] \| Non-Compete Agreements [Member]
Business Acquisition [Line Items]
Business acquisition not deductible for income tax purposes					16.7
Brokerage [Member] \| Trade Names [Member]
Business Acquisition [Line Items]
Business acquisition not deductible for income tax purposes					$ 0.5
Minimum [Member] \| Expiration Lists [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years					2 years
Minimum [Member] \| Non-Compete Agreements [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years					2 years
Minimum [Member] \| Trade Names [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years					2 years
Maximum [Member] \| Expiration Lists [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years					15 years
Maximum [Member] \| Non-Compete Agreements [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years					6 years
Maximum [Member] \| Trade Names [Member]
Business Acquisition [Line Items]
Estimated useful lives of intangibles assets, years					15 years
2024 Acquisitions [Member] \| Valuation, Market Approach [Member] \| Measurement Input, Discount Rate [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Measurement input					0.03
2024 Acquisitions [Member] \| Valuation, Market Approach [Member] \| Measurement Input, Discount Rate [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Measurement input					0.19
2024 Acquisitions [Member] \| Valuation, Market Approach [Member] \| Measurement Input, Long-term Revenue Growth Rate [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Measurement input					0.007
2024 Acquisitions [Member] \| Valuation, Market Approach [Member] \| Measurement Input, Long-term Revenue Growth Rate [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Measurement input					0.053
2024 Acquisitions [Member] \| Valuation, Income Approach [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Attrition rate					5.00%
2024 Acquisitions [Member] \| Valuation, Income Approach [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Attrition rate					13.50%
2024 Acquisitions [Member] \| Valuation, Income Approach [Member] \| Measurement Input, Discount Rate [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Measurement input					0.071
2024 Acquisitions [Member] \| Valuation, Income Approach [Member] \| Measurement Input, Discount Rate [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Measurement input					0.09
2024 Acquisitions [Member] \| Valuation, Income Approach [Member] \| Measurement Input, Long-term Revenue Growth Rate [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Measurement input					0.095
2024 Acquisitions [Member] \| Valuation, Income Approach [Member] \| Measurement Input, Long-term Revenue Growth Rate [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Measurement input					0.115
Business Acquisition [Member]
Business Acquisition [Line Items]
Annualized revenue of business acquisitions					$ 386.5
Total revenues					169.2
Net earnings					(18.0)
Net earnings before interest, income taxes, depreciation, amortization and change in estimated acquisition earnout payables					33.1
Business Acquisition [Member] \| Brokerage [Member]
Business Acquisition [Line Items]
Expiration lists					791.5
Non-compete agreements					23.6
Trade names					1.9
Deferred tax liability					$ 64.9
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
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
2023 Acquisitions [Member] \| Valuation, Income Approach [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Attrition rate					5.00%
2023 Acquisitions [Member] \| Valuation, Income Approach [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Attrition rate					13.50%
2023 Acquisitions [Member] \| Valuation, Income Approach [Member] \| Measurement Input, Long-term Revenue Growth Rate [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Measurement input					0.095
2023 Acquisitions [Member] \| Valuation, Income Approach [Member] \| Measurement Input, Long-term Revenue Growth Rate [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Measurement input					0.115
AssuredPartners, Inc [Member]
Business Acquisition [Line Items]
Gross consideration				$ 13,450.0
Cash raised through follow-on common stock offering			$ 8,500.0
Over-Allotment Option [Member] \| AssuredPartners, Inc [Member] \| Subsequent Event [Member]
Business Acquisition [Line Items]
Cash raised through follow-on common stock offering	$ 1,280.0
Senior Notes [Member] \| AssuredPartners, Inc [Member]
Business Acquisition [Line Items]
Cash borrowed from senior notes		$ 5,000.0