v3.25.4
Goodwill and Intangible Assets - Net (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Goodwill and Intangible Assets      
Gross carrying amount $ 10,403.3 $ 10,771.8  
Accumulated amortization (1,647.8) (2,033.4)  
Accumulated impairment and other (416.1) (460.2)  
Total 8,339.4 8,278.2 $ 6,376.3
Goodwill      
Goodwill and Intangible Assets      
Gross carrying amount 4,553.3 4,488.0  
Accumulated impairment and other (322.9) (363.1)  
Total 4,230.4 4,124.9 3,121.9
Lloyd's participation rights      
Goodwill and Intangible Assets      
Gross carrying amount 503.2 503.2  
Total 503.2 503.2 503.2
Customer and broker relationships      
Goodwill and Intangible Assets      
Gross carrying amount 2,064.7 2,039.4  
Accumulated amortization (942.5) (803.7)  
Accumulated impairment and other (28.5) (32.2)  
Total 1,093.7 1,203.5 1,070.6
Brand names      
Goodwill and Intangible Assets      
Gross carrying amount 1,997.3 1,901.3  
Accumulated amortization (31.1) (20.1)  
Accumulated impairment and other (34.7) (36.6)  
Total 1,931.5 1,844.6 1,169.9
Computer software and other      
Goodwill and Intangible Assets      
Gross carrying amount 1,284.8 1,839.9  
Accumulated amortization (674.2) (1,209.6)  
Accumulated impairment and other (30.0) (28.3)  
Total 580.6 602.0 510.7
Intangible assets other than goodwill      
Goodwill and Intangible Assets      
Gross carrying amount 5,850.0 6,283.8  
Accumulated amortization (1,647.8) (2,033.4)  
Accumulated impairment and other (93.2) (97.1)  
Total $ 4,109.0 $ 4,153.3 $ 3,254.4