Fair Value OF Financial Instrument - Quantitative Information about Significant Unobservable Inputs for Level 3 Recurring Fair Value Measurements (Details) $ in Millions	Mar. 31, 2026 USD ($)	Dec. 31, 2025 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Net MRBs	$ (6.2)	$ (9.0)	$ (5.2)	$ (6.8)
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 | 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]
Derivatives embedded in fixed indexed annuity products	$ 78.2	$ 82.1
Net MRBs	$ (6.2)	$ (9.0)