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Fair Value Measurement - Narrative (Details) - Security | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021
Assured IM |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Obligation to purchase debt | 0.05 |
Recurring | Level 3 |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Number of fixed maturity securities valued using model processes | 188 |
Recurring | Minimum | Credit Default Swap | Level 3 | Discount rate |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Conditional prepayment rate (as a percent) | 2.78% | 0.11%
Recurring | Maximum | Credit Default Swap | Level 3 | Discount rate |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Conditional prepayment rate (as a percent) | 5.08% | 1.78%

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- Definition Estimated rate of prepayment of principal on financial assets for initial fair value measurement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c)(2) -URI https://asc.fasb.org/extlink&oid=121570589&loc=d3e107207-111719 + Details
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