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Investments (Net Realized and Unrealized Investment Gains and (Losses)) (Details) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Gain (Loss) on Securities [Line Items] |  |
Gross gains on sales | $ 3,676 | $ 5,676
Gross losses on sales | (4,471) | (1,576)
Net realized investment gains (losses) on disposals | (795) | 4,100
Net unrealized gains (losses) on equity securities | 11,280 | (17,137)
Losses on securities for which we have the intent to sell | (362) | (15,602)
Net realized and unrealized investment gains (losses) | 5,119 | (44,666)
Available-for-sale Securities [Member] |  |
Gain (Loss) on Securities [Line Items] |  |
Net credit loss expense on fixed maturities | (4,997) | (15,787)
Held-to-maturity Securities [Member] |  |
Gain (Loss) on Securities [Line Items] |  |
Net credit loss expense on fixed maturities | (7) | 0
Commercial Mortgage Loans [Member] |  |
Gain (Loss) on Securities [Line Items] |  |
Net credit loss expense on fixed maturities | $ 0 | $ (240)

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