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Fair Value Measurement - Additional Information (Details) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2024 USD ($) security Trust | Dec. 31, 2023
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Number of fixed maturity debt securities classified as Level 3 | security | 1 |
Total |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Percentage of CDS contracts fair valued using minimum premium | 14.20% | 11.50%
AGC And AGM |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Number of custodial trusts | Trust | 4 |
Share value, amount | $ | $ 200 |
Maximum amount | $ | $ 50 |
Recurring | Level 3 |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Number of fixed maturity securities valued using model processes | security | 186 |
Recurring | Level 3 | CDR | Total | Minimum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Conditional prepayment rate | 3.44% | 3.26%
Recurring | Level 3 | CDR | Total | Maximum |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |
Conditional prepayment rate | 5.42% | 4.81%

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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 -Topic 860 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481326/860-20-50-3 + Details
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- Definition Amount that would be paid, determined under the conditions specified in the contract, if the holder of the share has the right to redeem the shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 480 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481648/480-10-50-2 + Details
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