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Investments (Unrealized Gains (Losses) on Equity Securities) (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2021 | Mar. 31, 2020
Gain (Loss) on Securities [Line Items] |  |
Unrealized gains (losses) recognized in income on equity securities on securities remaining in our portfolio at March 31, 2021 | $ 10,097 | $ (17,140)
Unrealized gains (losses) recognized in income on equity securities on securities sold during period | 1,183 | 3
Total unrealized gains (losses) recognized in income on equity securities | $ 11,280 | $ (17,137)

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