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Fair Value of Financial Instruments - Quantitative Information about Level 3 Fair Value Measurements (Details) $ in Millions | Jun. 30, 2023 USD ($) | Mar. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Jun. 30, 2022 USD ($) | Mar. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($)
--- | --- | --- | --- | --- | --- | --- | ---
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Fair Value | $ 5,211.9 |  | $ 5,185.0 |  |  |  |
Equity securities at fair value | 85.8 |  | 99.6 |  |  |  |
Net MRBs | (3.6) | $ 1.3 | 0.2 | $ 4.6 | $ 4.0 | $ 4.8 | $ 8.6
Fair Value | Recurring |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Fair Value | 5,211.9 |  | 5,185.0 |  |  |  |
Equity securities at fair value | 85.8 |  | 99.6 |  |  |  |
Municipal bonds |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Fair Value | 1,252.5 |  | 1,269.7 |  |  |  |
Municipal bonds | Fair Value | Recurring |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Fair Value | 1,252.6 |  | 1,269.7 |  |  |  |
Corporate bonds |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Fair Value | 1,828.4 |  | 1,901.7 |  |  |  |
Corporate bonds | Fair Value | Recurring |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Fair Value | 1,828.4 |  | 1,901.7 |  |  |  |
Level 3 | Fair Value | Recurring |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Fair Value | 476.8 |  | 423.3 |  |  |  |
Equity securities at fair value | 2.0 |  | 2.0 |  |  |  |
Derivatives embedded in fixed indexed annuity products | 87.2 |  |  |  |  |  |
Net MRBs | (3.6) |  |  |  |  |  |
Level 3 | Municipal bonds | Fair Value | Recurring |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Fair Value | $ 63.9 |  | 54.4 |  |  |  |
Level 3 | Municipal bonds | discounted cash flow | option adjusted spread |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.0308 |  |  |  |  |  |
Level 3 | Corporate bonds | Fair Value | Recurring |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Fair Value | $ 311.5 |  | $ 261.3 |  |  |  |
Level 3 | Corporate bonds | discounted cash flow | option adjusted spread |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.0241 |  |  |  |  |  |
Level 3 | Corporate bonds | discounted cash flow | exit cap |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 6.2 |  |  |  |  |  |
Level 3 | Corporate bonds | vendor priced | vendor priced |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 79.64 |  |  |  |  |  |
Level 3 | Corporate bonds | market comparable | EV / Fwd EBITDA (x) |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 5.92 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | Fair Value |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Fair Value | $ 101.4 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | LIBOR |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.023 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | discount margin |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.395 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | PDI spread |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.055 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | SBL spread |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.045 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | CPR |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.200 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | default rate annual |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.040 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | recovery |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.650 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | I spread |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.0175 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | N spread |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.0463 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | T Spread |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.0226 |  |  |  |  |  |
Level 3 | Mortgage-backed and other asset-backed securities | market comparable | median price |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 81.34 |  |  |  |  |  |
Minimum | Level 3 | discounted cash flow | option budget |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Derivatives embedded in fixed indexed annuity products, measurement input | 0.009 |  |  |  |  |  |
Minimum | Level 3 | market comparable | price/book ExAOCI |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Equity securities, measurement input | 1.06 |  |  |  |  |  |
Minimum | Level 3 | black-scholes | volatility |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Equity securities, measurement input | 0.280 |  |  |  |  |  |
Minimum | Level 3 | black-scholes | time to exit |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Equity securities, measurement input | 0.000267 |  |  |  |  |  |
Minimum | Level 3 | Corporate bonds | discounted cash flow | yield |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.061 |  |  |  |  |  |
Minimum | Level 3 | Corporate bonds | discounted cash flow | discount rate |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 6.2 |  |  |  |  |  |
Minimum | Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | yield |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.064 |  |  |  |  |  |
Minimum | Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | discount rate |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.160 |  |  |  |  |  |
Minimum | Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | median comparable yield |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.207 |  |  |  |  |  |
Minimum | Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | weighting |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.170 |  |  |  |  |  |
Minimum | Level 3 | Mortgage-backed and other asset-backed securities | vendor priced | haircut |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.0001 |  |  |  |  |  |
Maximum | Level 3 | discounted cash flow | option budget |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Derivatives embedded in fixed indexed annuity products, measurement input | 0.038 |  |  |  |  |  |
Maximum | Level 3 | black-scholes | volatility |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Equity securities, measurement input | 0.440 |  |  |  |  |  |
Maximum | Level 3 | Corporate bonds | discounted cash flow | yield |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 11.0 |  |  |  |  |  |
Maximum | Level 3 | Corporate bonds | discounted cash flow | discount rate |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 10.7 |  |  |  |  |  |
Maximum | Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | yield |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.065 |  |  |  |  |  |
Maximum | Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | discount rate |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.210 |  |  |  |  |  |
Maximum | Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | median comparable yield |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.432 |  |  |  |  |  |
Maximum | Level 3 | Mortgage-backed and other asset-backed securities | discounted cash flow | weighting |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.830 |  |  |  |  |  |
Maximum | Level 3 | Mortgage-backed and other asset-backed securities | vendor priced | haircut |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Debt securities, measurement input | 0.003 |  |  |  |  |  |
Weighted Average | Level 3 | discounted cash flow | lapse rate |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Derivatives embedded in fixed indexed annuity products, measurement input | 0.054 |  |  |  |  |  |
Net MRBs, measurement input | 0.053 |  |  |  |  |  |
Weighted Average | Level 3 | discounted cash flow | mortality multiplier |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Derivatives embedded in fixed indexed annuity products, measurement input | 0.678 |  |  |  |  |  |
Net MRBs, measurement input | 0.678 |  |  |  |  |  |
Weighted Average | Level 3 | discounted cash flow | non-performance adjustment |  |  |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques |  |  |  |  |  |  |
Derivatives embedded in fixed indexed annuity products, measurement input | 0.050 |  |  |  |  |  |

X
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- Definition Amount, before effect of reinsurance and after accumulated increase (decrease) in instrument-specific credit risk, of contract or contract feature in long-duration contract issued by insurance entity that both protects contract holder from other-than-nominal capital market risk and exposes insurance entity to other-than-nominal capital market risk. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (h)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29G -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29G Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 7B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-7B Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 45 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480112/944-40-45-3 + Details
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