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Investments (Narrative) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 USD ($) securities | Dec. 31, 2023 USD ($) securities
Investments, Debt and Equity Securities [Abstract] |  |
Available-for-sale fixed maturity securities in unrealized loss position, number of positions | securities | 1,485 | 1,386
Available-for-sale fixed maturity securities in unrealized loss position, number of positions, 12 months or longer | securities | 966 | 1,131
Available-for-sale fixed maturity securities, estimated fair value | $ 12,570,401 | $ 9,982,329
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | 743,003 | 661,282
Available-for-sale fixed maturity securities, estimated fair value, 12 months or longer | 7,448,033 | 8,515,061
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | $ 633,124 | $ 650,461
Estimated average duration of fixed maturities | 3 years 10 months 24 days |
Percentage threshold of shareholders' equity used to define concentration of investments | 10.00% | 10.00%

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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 55 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479081/326-30-55-8 Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-7 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479106/326-30-50-5 + Details
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