v3.25.4
Cash and Investments - Fair value assets valuation (Details)
$ in Millions
12 Months Ended
Dec. 31, 2025
USD ($)
item
$ / a
$ / ft²
Dec. 31, 2024
USD ($)
item
Dec. 31, 2023
USD ($)
Private placement debt securities      
Cash and Investments      
Number of investments | item 11 11  
Private placement debt securities | Sensitivity Analysis, increase in credit spreads      
Cash and Investments      
Percentage of reasonably possible increase in unobservable input, assets 1.00%    
Increase (decrease) in fair value measurement due to reasonably possible decrease in unobservable input, assets $ 43.0    
Private placement debt securities | Sensitivity Analysis, decrease in credit spreads      
Cash and Investments      
Increase (decrease) in fair value measurement due to reasonably possible increase in unobservable input, assets $ (43.6)    
Percentage of reasonably possible decrease in unobservable input, assets 1.00%    
Private placement debt securities | Discounted cash flow | Credit spread | Low      
Cash and Investments      
Significant unobservable input 0.027    
Private placement debt securities | Discounted cash flow | Credit spread | High      
Cash and Investments      
Significant unobservable input 0.095    
Private placement debt securities - largest investment | Construction and home building      
Cash and Investments      
Financial assets   $ 125.6  
Private placement debt securities - largest investment | Orla Mining Limited      
Cash and Investments      
Financial assets $ 369.3    
Private placement debt securities - second largest investment | Blizzard Vacatia      
Cash and Investments      
Financial assets 365.0    
Private placement debt securities - second largest investment | Amynta Group      
Cash and Investments      
Financial assets   121.0  
Private placement debt securities - third largest investment | Blizzard Vacatia      
Cash and Investments      
Financial assets $ 275.0    
Private placement debt securities - third largest investment | Duke Capital Limited      
Cash and Investments      
Financial assets   $ 114.6  
Mortgage loans      
Cash and Investments      
Number of investments | item 112 93  
Mortgage loans | Sensitivity Analysis, increase in credit spreads      
Cash and Investments      
Percentage of reasonably possible increase in unobservable input, assets 1.00%    
Increase (decrease) in fair value measurement due to reasonably possible increase in unobservable input, assets $ (38.1)    
Mortgage loans | Sensitivity Analysis, decrease in credit spreads      
Cash and Investments      
Percentage of reasonably possible decrease in unobservable input, assets 1.00%    
Increase (decrease) in fair value measurement due to reasonably possible decrease in unobservable input, assets $ 10.1    
Mortgage loans | Discounted cash flow | Credit spread | Low      
Cash and Investments      
Significant unobservable input 0.023    
Mortgage loans | Discounted cash flow | Credit spread | High      
Cash and Investments      
Significant unobservable input 0.098    
Mortgage loans - largest investment      
Cash and Investments      
Financial assets $ 374.2 $ 235.0  
Private placement preferred shares      
Cash and Investments      
Number of investments | item 3 2  
Private placement preferred shares | Sensitivity Analysis, increase in credit spreads      
Cash and Investments      
Percentage of reasonably possible increase in unobservable input, assets 1.00%    
Private placement preferred shares | Sensitivity Analysis, decrease in credit spreads      
Cash and Investments      
Increase (decrease) in fair value measurement due to reasonably possible increase in unobservable input, assets $ (49.5)    
Percentage of reasonably possible decrease in unobservable input, assets 1.00%    
Increase (decrease) in fair value measurement due to reasonably possible decrease in unobservable input, assets $ 74.3    
Private placement preferred shares | Discounted cash flow | Credit spread | Low      
Cash and Investments      
Significant unobservable input 0.027    
Private placement preferred shares | Discounted cash flow | Credit spread | High      
Cash and Investments      
Significant unobservable input 0.046    
Private placement preferred shares | Global Containership Owner Operator      
Cash and Investments      
Financial assets $ 299.2    
Private placement preferred shares | Real Estate Management And Development      
Cash and Investments      
Financial assets   $ 191.0  
Limited partnerships and other      
Cash and Investments      
Number of investments | item 45 44  
Limited partnerships and other | Sensitivity Analysis, increase in net asset values      
Cash and Investments      
Percentage of reasonably possible increase in unobservable input, assets 10.00%    
Increase (decrease) in fair value measurement due to reasonably possible decrease in unobservable input, assets $ 228.4    
Limited partnerships and other | Sensitivity Analysis, decrease in net asset values      
Cash and Investments      
Increase (decrease) in fair value measurement due to reasonably possible increase in unobservable input, assets $ (228.4)    
Percentage of reasonably possible decrease in unobservable input, assets 10.00%    
Limited partnerships and other | Industrials One      
Cash and Investments      
Financial assets $ 488.8 $ 320.1  
Limited partnerships and other | Industrials Two      
Cash and Investments      
Financial assets 283.5 265.6  
Limited partnerships and other | Industrials Three      
Cash and Investments      
Financial assets $ 261.6    
Limited partnerships and other | Oil and gas extraction      
Cash and Investments      
Financial assets   288.4  
Investment property | Sales comparison | Discount rate | Low      
Cash and Investments      
Significant unobservable input 0.18    
Investment property | Sales comparison | Discount rate | High      
Cash and Investments      
Significant unobservable input 0.18    
Investment property | Sales comparison | Price per acre (Cdn$ thousands) | Low      
Cash and Investments      
Price per acre (Cdn$ thousands) | $ / a 40,200    
Investment property | Sales comparison | Price per acre (Cdn$ thousands) | High      
Cash and Investments      
Price per acre (Cdn$ thousands) | $ / a 183,600    
Investment property | Sales comparison | Price per square foot (US$) | Low      
Cash and Investments      
Price per square foot (US$) | $ / ft² 120    
Investment property | Sales comparison | Price per square foot (US$) | High      
Cash and Investments      
Price per square foot (US$) | $ / ft² 120    
Investment property | Income capitalization | Terminal capitalization rate | Low      
Cash and Investments      
Significant unobservable input 0.063    
Investment property | Income capitalization | Terminal capitalization rate | High      
Cash and Investments      
Significant unobservable input 0.09    
Investment property | Income capitalization | Discount rate | Low      
Cash and Investments      
Significant unobservable input 0.08    
Investment property | Income capitalization | Discount rate | High      
Cash and Investments      
Significant unobservable input 0.103    
Investment property | Income capitalization | Market rent growth rate | Low      
Cash and Investments      
Significant unobservable input 0.022    
Investment property | Income capitalization | Market rent growth rate | High      
Cash and Investments      
Significant unobservable input 0.03    
Investment property | Income capitalization | Overall capitalization rate | Low      
Cash and Investments      
Significant unobservable input 0.055    
Investment property | Income capitalization | Overall capitalization rate | High      
Cash and Investments      
Significant unobservable input 0.055    
Level 3      
Cash and Investments      
Financial assets $ 11,984.0 10,059.0 $ 11,460.0
Level 3 | Bonds      
Cash and Investments      
Financial assets 7,050.4    
Level 3 | Private placement debt securities      
Cash and Investments      
Financial assets 7,050.4 5,762.6 5,797.0
Level 3 | Private placement debt securities | Discounted cash flow      
Cash and Investments      
Financial assets 1,520.1    
Level 3 | Mortgage loans | Market approach and discounted cash flow      
Cash and Investments      
Financial assets 5,402.5    
Level 3 | Other | Various      
Cash and Investments      
Financial assets 127.8    
Level 3 | Preferred Stocks      
Cash and Investments      
Financial assets 758.2    
Level 3 | Private placement preferred shares | Discounted cash flow      
Cash and Investments      
Financial assets 676.6    
Level 3 | Other | Various      
Cash and Investments      
Financial assets 81.6    
Level 3 | Common Stocks      
Cash and Investments      
Financial assets 3,389.4    
Level 3 | Limited partnerships and other      
Cash and Investments      
Financial assets 2,284.0 $ 2,104.8 $ 1,998.2
Level 3 | Limited partnerships and other | Net asset value      
Cash and Investments      
Financial assets 2,284.0    
Level 3 | Private equity funds | Net asset value      
Cash and Investments      
Financial assets 492.4    
Level 3 | Other | Various      
Cash and Investments      
Financial assets 613.0    
Level 3 | Derivatives and other invested assets      
Cash and Investments      
Financial assets 734.8    
Level 3 | Derivatives and other invested assets | Various      
Cash and Investments      
Financial assets 51.2    
Level 3 | Investment property | Sales comparison      
Cash and Investments      
Financial assets 215.1    
Level 3 | Investment property | Income capitalization      
Cash and Investments      
Financial assets 383.2    
Level 3 | Other | Various      
Cash and Investments      
Financial assets $ 136.5