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Net Investment Gains (Losses) (Change in Unrealized Gains (Losses) of Available For Sales Securities) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Realized and Unrealized Investment Gains Losses [Line Items] |  |  |
Unrealized investment gains, before tax | $ 392,903 | $ (1,248,128) | $ (254,939)
Income tax (expense) benefit | (86,350) | 264,325 | 56,127
Noncontrolling interests | (2) | (2) | (2)
Total change in unrealized gains and losses | 306,551 | (983,805) | (198,814)
Debt Securities |  |  |
Realized and Unrealized Investment Gains Losses [Line Items] |  |  |
Unrealized investment gains, before tax | 389,839 | (1,216,292) | (262,221)
Fixed maturity securities with allowance for expected credit losses |  |  |
Realized and Unrealized Investment Gains Losses [Line Items] |  |  |
Unrealized investment gains, before tax | 643 | (28,370) | 10,124
Investment funds |  |  |
Realized and Unrealized Investment Gains Losses [Line Items] |  |  |
Unrealized investment gains, before tax | 3,989 | (2,019) | (1,270)
Other |  |  |
Realized and Unrealized Investment Gains Losses [Line Items] |  |  |
Unrealized investment gains, before tax | $ (1,568) | $ (1,447) | $ (1,572)

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