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Investments (Summary Of Net Investment Gains (Losses) And The Change In Net Unrealized Gains On Investments) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019
Gain (Loss) on Securities [Line Items] |  |  |  |
Cost method investments, realized gains | $ 0 | $ 0 | $ 11,167 | $ 0
Net realized investment gains (losses) | (2,812) | (67) | 6,926 | 614
Change in fair value of equity securities sold during the period | 82,523 | 202 | 43,458 | 26,616
Change in fair value of equity securities held at the end of the period | 831,532 | 425,518 | (820,582) | 1,010,614
Total change in fair value of equity securities | 914,055 | 425,720 | (777,124) | 1,037,230
Net investment gains (losses) | 911,243 | 425,653 | (770,198) | 1,037,844
Change in net unrealized gains on available-for-sale investments included in other comprehensive income | 216,909 | 163,816 | 295,898 | 356,652
Reserve deficiency adjustment for life and annuity benefit reserves | (22,740) | (35,938) | (35,612) | (61,751)
Sales of fixed maturities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Fixed maturity securities, realized gains | 5,348 | 1,661 | 6,733 | 1,804
Fixed maturity securities, realized losses | (5,126) | (630) | (6,271) | (911)
Change in allowance for expected credit losses | 1,537 | 0 | (202) | 0
Sales of short-term investments [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Short-term investments, available-for-sale, realized gain | 1,002 | 499 | 1,100 | 1,334
Short-term investments, available-for-sale, realized loss | (184) | (2,049) | (356) | (2,073)
Fixed Maturities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Change in net unrealized gains on available-for-sale investments included in other comprehensive income | 236,521 | 197,248 | 335,088 | 414,542
Short-term investments [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Change in net unrealized gains on available-for-sale investments included in other comprehensive income | 3,128 | 2,506 | (3,578) | 3,861
Sales of Other Investments |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Other investment gains (losses) | $ (5,389) | $ 452 | $ (5,245) | $ 460

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