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Investments (Unrealized Gains on Investments) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Net unrealized (losses) gains | $ (353,253) | $ (527,891) | $ 228,963
Deferred income tax | 74,184 | 110,857 | (48,082)
Net unrealized (losses) gains, net of deferred income tax | (279,069) | (417,034) | 180,881
Increase (decrease) in net unrealized gains (losses) in OCI, net of deferred income tax | 137,965 | (597,915) | (124,370)
Available-for-sale Securities [Member] |  |  |
Net unrealized (losses) gains | (353,288) | (527,926) | 228,947
Total HTM Securities [Member] |  |  |
Net unrealized (losses) gains | 0 | 0 | (4)
Short-term Investments [Member] |  |  |
Net unrealized (losses) gains | $ 35 | $ 35 | $ 20

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