v3.25.4
Goodwill and Intangible Assets - Allocation to CGUs (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of information for cash-generating units      
Goodwill $ 4,230.4 $ 4,124.9  
Intangible assets 4,109.0 4,153.3  
Total $ 8,339.4 8,278.2 $ 6,376.3
Minimum      
Disclosure of information for cash-generating units      
Growth rate used to extrapolate cash flow projections 2.30%    
Maximum      
Disclosure of information for cash-generating units      
Growth rate used to extrapolate cash flow projections 3.70%    
Insurance and reinsurance companies      
Disclosure of information for cash-generating units      
Goodwill $ 2,189.4 2,181.4  
Intangible assets 1,834.2 1,915.1  
Total $ 4,023.6 4,096.5  
Insurance and reinsurance companies | Minimum      
Disclosure of information for cash-generating units      
Discount rate applied to cash flow projections 9.80%    
Investment return rate 5.00%    
Insurance and reinsurance companies | Maximum      
Disclosure of information for cash-generating units      
Discount rate applied to cash flow projections 11.80%    
Investment return rate 7.00%    
Allied World      
Disclosure of information for cash-generating units      
Goodwill $ 940.0 940.0  
Intangible assets 387.6 431.0  
Total 1,327.6 1,371.0  
Gulf Insurance      
Disclosure of information for cash-generating units      
Goodwill 346.3 346.6  
Intangible assets 513.4 542.9  
Total 859.7 889.5  
Brit      
Disclosure of information for cash-generating units      
Goodwill 169.1 167.3  
Intangible assets 520.9 521.6  
Total 690.0 688.9  
Zenith National      
Disclosure of information for cash-generating units      
Goodwill 317.6 317.6  
Intangible assets 55.0 62.6  
Total 372.6 380.2  
Crum & Forster      
Disclosure of information for cash-generating units      
Goodwill 132.6 132.6  
Intangible assets 73.3 84.0  
Total 205.9 216.6  
Northbridge      
Disclosure of information for cash-generating units      
Goodwill 77.8 76.9  
Intangible assets 101.6 110.9  
Total 179.4 187.8  
Odyssey Group      
Disclosure of information for cash-generating units      
Goodwill 107.9 107.9  
Intangible assets 56.2 49.8  
Total 164.1 157.7  
All other      
Disclosure of information for cash-generating units      
Goodwill 98.1 92.5  
Intangible assets 126.2 112.3  
Total 224.3 204.8  
Non-insurance companies      
Disclosure of information for cash-generating units      
Goodwill 2,041.0 1,943.5  
Intangible assets 2,274.8 2,238.2  
Total $ 4,315.8 4,181.7  
Non-insurance companies | Minimum      
Disclosure of information for cash-generating units      
Discount rate applied to cash flow projections 10.70%    
Non-insurance companies | Maximum      
Disclosure of information for cash-generating units      
Discount rate applied to cash flow projections 14.70%    
Recipe      
Disclosure of information for cash-generating units      
Goodwill $ 266.6 264.0  
Intangible assets 899.7 835.3  
Total 1,166.3 1,099.3  
Sleep Country      
Disclosure of information for cash-generating units      
Goodwill 613.8 517.3  
Intangible assets 455.3 398.3  
Total 1,069.1 915.6  
Peak Achievement Athletics, Inc.      
Disclosure of information for cash-generating units      
Goodwill 270.9 279.0  
Intangible assets 434.7 443.0  
Total 705.6 722.0  
Meadow Foods      
Disclosure of information for cash-generating units      
Goodwill 240.0 222.0  
Intangible assets 320.6 322.2  
Total 560.6 544.2  
AGT      
Disclosure of information for cash-generating units      
Goodwill 154.4 148.2  
Intangible assets 58.4 55.5  
Total 212.8 203.7  
Thomas Cook India      
Disclosure of information for cash-generating units      
Goodwill 117.5 123.4  
Intangible assets 51.9 46.0  
Total 169.4 169.4  
Boat Rocker      
Disclosure of information for cash-generating units      
Goodwill   29.4  
Intangible assets   78.1  
Total   107.5  
All other      
Disclosure of information for cash-generating units      
Goodwill 377.8 360.2  
Intangible assets 54.2 59.8  
Total $ 432.0 $ 420.0