Fair Value of Financial Instruments - Quantitative Information about Level 3 Fair Value Measurements (Details) | Mar. 31, 2022USD ($) | Dec. 31, 2021USD ($) |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, available-for-sale | $ 5,987,400,000 | $ 6,239,300,000 |
Equity securities at fair value | 126,800,000 | 147,200,000 |
Carrying Amount | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Equity securities at fair value | 126,800,000 | 147,200,000 |
Municipal bonds | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, available-for-sale | 1,579,500,000 | 1,703,400,000 |
Municipal bonds | Carrying Amount | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, available-for-sale | 1,579,500,000 | 1,703,400,000 |
Corporate bonds | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, available-for-sale | 2,296,000,000 | 2,388,700,000 |
Corporate bonds | Carrying Amount | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, available-for-sale | $ 2,296,000,000 | 2,388,700,000 |
Other asset-backed securities | Carrying Amount | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, available-for-sale | | $ 1,075,200,000 |
Level 3 | discounted cash flow | volatility | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Equity securities, measurement input | 100 | |
Level 3 | discounted cash flow | volatility | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Equity securities, measurement input | 121.95 | |
Level 3 | discounted cash flow | lapse rate | Weighted Average | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Derivatives embedded in fixed indexed annuity products, measurement input | 0.053 | |
Level 3 | discounted cash flow | mortality multiplier | Weighted Average | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Derivatives embedded in fixed indexed annuity products, measurement input | 0.668 | |
Level 3 | discounted cash flow | option budget | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Derivatives embedded in fixed indexed annuity products, measurement input | 0.009 | |
Level 3 | discounted cash flow | option budget | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Derivatives embedded in fixed indexed annuity products, measurement input | 0.025 | |
Level 3 | discounted cash flow | non-performance adjustment | Weighted Average | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Derivatives embedded in fixed indexed annuity products, measurement input | 0.050 | |
Level 3 | Municipal bonds | discounted cash flow | I Spread | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.0360 | |
Level 3 | Municipal bonds | discounted cash flow | I Spread | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.0409 | |
Level 3 | Corporate bonds | discounted cash flow | N Spread | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.0213 | |
Level 3 | Corporate bonds | discounted cash flow | N Spread | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.0379 | |
Level 3 | Corporate bonds | discounted cash flow | T spread | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 100 | |
Level 3 | Corporate bonds | discounted cash flow | T spread | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 560 | |
Level 3 | Corporate bonds | discounted cash flow | yield | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.027 | |
Level 3 | Corporate bonds | discounted cash flow | yield | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.107 | |
Level 3 | Corporate bonds | discounted cash flow | discount rate | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.113 | |
Level 3 | Corporate bonds | discounted cash flow | discount rate | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.120 | |
Level 3 | Corporate bonds | market comparable | option adjusted spread | Weighted Average | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.125 | |
Level 3 | Other asset-backed securities | discounted cash flow | N Spread | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.0213 | |
Level 3 | Other asset-backed securities | discounted cash flow | N Spread | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.0379 | |
Level 3 | Other asset-backed securities | discounted cash flow | T spread | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.0100 | |
Level 3 | Other asset-backed securities | discounted cash flow | T spread | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.0560 | |
Level 3 | Other asset-backed securities | discounted cash flow | discount rate | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.085 | |
Level 3 | Other asset-backed securities | discounted cash flow | discount rate | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.200 | |
Level 3 | Other asset-backed securities | discounted cash flow | discount margin | Weighted Average | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.146 | |
Level 3 | Other asset-backed securities | discounted cash flow | median comparable yield | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.100 | |
Level 3 | Other asset-backed securities | discounted cash flow | median comparable yield | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.220 | |
Level 3 | Other asset-backed securities | market comparable | median price | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 28.54 | |
Level 3 | Other asset-backed securities | market comparable | median price | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 92.06 | |
Level 3 | Other asset-backed securities | vendor price | haircut | Minimum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.030 | |
Level 3 | Other asset-backed securities | vendor price | haircut | Maximum | | |
Fair Value Measurement Inputs and Valuation Techniques | | |
Debt securities, measurement input | 0.050 | |