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Investments (Narrative) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2023 USD ($) securities | Dec. 31, 2022 USD ($) securities
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale fixed maturity securities in unrealized loss position, number of positions | securities | 1,386 | 1,400
Available-for-sale fixed maturity securities in unrealized loss position, number of positions, 12 months or longer | securities | 1,131 | 246
Available-for-sale fixed maturity securities, estimated fair value | $ 9,982,329 | $ 11,280,896
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | 661,282 | 962,210
Available-for-sale fixed maturity securities, estimated fair value, 12 months or longer | 8,515,061 | 3,356,273
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | $ 650,461 | $ 393,911
Estimated average duration of fixed maturities | 4 years 1 month 6 days |
Percentage threshold of shareholders' equity used to define concentration of investments | 10.00% | 10.00%
Investments, Available-for-sale, Allowance for Credit Loss | $ 0 | $ 0
Fixed maturities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale fixed maturity securities, estimated fair value | 9,929,728 | 10,506,416
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | 660,889 | 962,152
Available-for-sale fixed maturity securities, estimated fair value, 12 months or longer | 8,515,061 | 3,356,273
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | $ 650,461 | $ 393,911

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