v3.26.1
Investments - Summary of Investment Income (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Investment income $ 336.3 $ 329.5 $ 287.3
Gain (loss) on investments 61.4 52.6 75.9
Investment expenses (10.0) (11.5) (11.6)
Net investment income 326.3 [1] 318.0 275.7
Fixed income securities — Available for sale      
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Investment income 214.2 161.5 115.7
Fixed income securities — Trading      
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Investment income 65.9 88.2 98.9
Short-term investments — Available for sale      
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Investment income 3.7 4.5 5.3
Short-term investments — Trading      
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Investment income 0.3 0.1 0.3
Fixed term deposits (included in cash and cash equivalents)      
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Investment income 39.1 45.3 39.9
Catastrophe bonds — Trading      
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Investment income 0.0 0.0 0.2
Privately-held investments — Available for sale      
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Investment income 1.9 1.2 0.1
Privately-held investments — Trading      
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Investment income 16.7 34.9 44.7
Equity Securities      
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Investment income 0.3 0.0 0.0
Other investments, at fair value      
Schedule of Investment Income, Reported Amounts, by Category [Line Items]      
Gain (loss) on investments $ 5.8 $ 6.2 $ (17.8)
[1] Net investment income includes related party net investment income of $13.6 million (2024 — $15.2 million, 2023 — $19.6 million) and related party investment management fees of $6.4 million (2024 — $9.2 million, 2023 — $9.4 million).