v3.26.1
Fair Value OF Financial Instrument - Quantitative Information about Significant Unobservable Inputs for Level 3 Recurring Fair Value Measurements (Details)
$ in Millions
Jun. 30, 2026
USD ($)
Mar. 31, 2026
USD ($)
Dec. 31, 2025
USD ($)
Jun. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Fair Value $ 5,767.0   $ 5,714.6      
Net MRBs (11.1) $ (6.2) (9.0) $ (6.7) $ (5.2) $ (6.8)
Fair Value            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Fair Value 5,767.0   5,714.6      
Fair Value | Corporate bonds            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Fair Value $ 1,954.5   $ 1,910.3      
Level 3 | Minimum | yield | discounted cash flow | Corporate bonds            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Corporate bonds, measurement input 0.035          
Level 3 | Minimum | option adjusted spread | discounted cash flow | Corporate bonds            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Corporate bonds, measurement input 0          
Level 3 | Minimum | option budget | discounted cash flow            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Derivatives embedded in fixed indexed annuity products, measurement input 0.009   0.009      
Level 3 | Maximum | yield | discounted cash flow | Corporate bonds            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Corporate bonds, measurement input 0.103          
Level 3 | Maximum | option adjusted spread | discounted cash flow | Corporate bonds            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Corporate bonds, measurement input 0.1086          
Level 3 | Maximum | option budget | discounted cash flow            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Derivatives embedded in fixed indexed annuity products, measurement input 0.039   0.039      
Level 3 | Weighted Average | lapse rate | discounted cash flow            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Derivatives embedded in fixed indexed annuity products, measurement input 0.075   0.075      
Net MRBs, measurement input 0.075   0.075      
Level 3 | Weighted Average | mortality multiplier | discounted cash flow            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Derivatives embedded in fixed indexed annuity products, measurement input 0.710   0.710      
Net MRBs, measurement input 0.710   0.710      
Level 3 | Weighted Average | non-performance adjustment | discounted cash flow            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Derivatives embedded in fixed indexed annuity products, measurement input 0.050   0.050      
Level 3 | Fair Value            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Fair Value $ 440.6   $ 465.3      
Level 3 | Fair Value | Corporate bonds            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Fair Value 321.9   342.6      
Level 3 | Fair Value | yield | discounted cash flow | Corporate bonds            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Fair Value 193.7          
Level 3 | Fair Value | lapse rate | discounted cash flow            
Fair Value Measurement Inputs and Valuation Techniques [Line Items]            
Derivatives embedded in fixed indexed annuity products 83.4   82.1      
Net MRBs $ (11.1)   $ (9.0)