v3.26.3
Business Combinations - Additional Information (Detail)
$ in Millions
 3 Months Ended 9 Months Ended
Aug. 18, 2025
USD ($)
segment
Sep. 30, 2026
USD ($)
acquisition
Mar. 31, 2026
USD ($)
Sep. 30, 2025
USD ($)
acquisition
Sep. 30, 2026
USD ($)
acquisition
Sep. 30, 2025
USD ($)
acquisition
Business Combination [Line Items]            
Accretion of the discount on acquisition   $ 9   $ 12 $ 33 $ 36
Income (expense) related to net adjustments to estimated fair value of liability for earnout obligations   $ (7)   $ (17) $ (6) $ (3)
Number of companies acquired | acquisition   30   41 94 82
Aggregate amount of maximum earnout obligations related to acquisitions   $ 1,360     $ 1,360  
Aggregate amount of maximum earnout obligations related to acquisitions, recorded in consolidated balance sheet   590     590  
Aggregate amount of earnout obligation expected settlement in cash or stock at option   459     459  
Aggregate amount of earnout obligation expected settlement in cash   131     131  
Goodwill   666     666  
Expiration lists   601     601  
Non-compete agreements   5     5  
Trade names   1     1  
Total revenues   3,979   $ 3,418 12,829 $ 10,472
Expiration Lists            
Business Combination [Line Items]            
Business acquisition not deductible for income tax purposes   286     286  
Non-Compete Agreements            
Business Combination [Line Items]            
Business acquisition not deductible for income tax purposes   5     5  
Trade Names            
Business Combination [Line Items]            
Business acquisition not deductible for income tax purposes   1     1  
Brokerage            
Business Combination [Line Items]            
Write-off of amortizable intangible assets   7   $ 2 29 $ 43
Brokerage Management            
Business Combination [Line Items]            
Goodwill   666     666  
Expiration lists   601     601  
Non-compete agreements   $ 5     $ 5  
Minimum            
Business Combination [Line Items]            
Business combination, earnout payable evaluation period         2 years  
Minimum | Expiration Lists            
Business Combination [Line Items]            
Estimated useful lives of intangibles assets, years   2 years     2 years  
Minimum | Non-Compete Agreements            
Business Combination [Line Items]            
Estimated useful lives of intangibles assets, years   2 years     2 years  
Minimum | Trade Names            
Business Combination [Line Items]            
Estimated useful lives of intangibles assets, years   2 years     2 years  
Maximum            
Business Combination [Line Items]            
Business combination, earnout payable evaluation period         3 years  
Maximum | Expiration Lists            
Business Combination [Line Items]            
Estimated useful lives of intangibles assets, years   15 years     15 years  
Maximum | Non-Compete Agreements            
Business Combination [Line Items]            
Estimated useful lives of intangibles assets, years   6 years     6 years  
Maximum | Trade Names            
Business Combination [Line Items]            
Estimated useful lives of intangibles assets, years   15 years     15 years  
AssuredPartners, Inc            
Business Combination [Line Items]            
Gross consideration $ 13,800          
Number of employees | segment 10,900          
Business combination, initial accounting incomplete, adjustment of goodwill     $ 220      
AssuredPartners, Inc | Expiration Lists            
Business Combination [Line Items]            
Business combination, initial accounting incomplete, adjustment of intangible assets     (222)      
AssuredPartners, Inc | Trade Names            
Business Combination [Line Items]            
Business combination, initial accounting incomplete, adjustment of intangible assets     $ 2      
Business Acquisition            
Business Combination [Line Items]            
Expiration lists   $ 601     $ 601  
Non-compete agreements   5     5  
Trade names   1     1  
Deferred tax liability   $ 71     71  
Annualized revenue of business acquisitions         224  
Total revenues         92  
Net earnings         (10)  
Net earnings before interest, income taxes, depreciation, amortization and change in estimated acquisition earnout payables         $ (17)  
2026 Acquisitions | Valuation, Market Approach | Measurement Input, Discount Rate | Minimum            
Business Combination [Line Items]            
Measurement input   0.030     0.030  
2026 Acquisitions | Valuation, Market Approach | Measurement Input, Discount Rate | Maximum            
Business Combination [Line Items]            
Measurement input   0.150     0.150  
2026 Acquisitions | Valuation, Income Approach | Measurement Input, Discount Rate | Minimum            
Business Combination [Line Items]            
Measurement input   0.070     0.070  
2026 Acquisitions | Valuation, Income Approach | Measurement Input, Discount Rate | Maximum            
Business Combination [Line Items]            
Measurement input   0.090     0.090  
2025 Acquisitions | Valuation, Market Approach | Measurement Input, Long-term Revenue Growth Rate | Minimum            
Business Combination [Line Items]            
Measurement input   0.030     0.030  
2025 Acquisitions | Valuation, Income Approach | Minimum            
Business Combination [Line Items]            
Attrition rate         5.00%  
2025 Acquisitions | Valuation, Income Approach | Maximum            
Business Combination [Line Items]            
Attrition rate         12.00%  
2025 Acquisitions | Valuation, Income Approach | Measurement Input, Long-term Revenue Growth Rate | Minimum            
Business Combination [Line Items]            
Measurement input   0.090     0.090  
2025 Acquisitions | Valuation, Income Approach | Measurement Input, Long-term Revenue Growth Rate | Maximum            
Business Combination [Line Items]            
Measurement input   0.120     0.120