Investments - Realized Investment Gains (Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Miscellaneous:
Net realized investment gains (losses)	$ 804	$ (10,806)
Available-for-sale securities
Available-for-sale securities:
Gross realized gains	1,923	1,074
Gross realized losses	(440)	(459)
Net realized gains on available-for-sale securities	1,483	615
Equity securities
Equity securities:
Equity securities	(679)	(11,422)
Miscellaneous
Miscellaneous:
Miscellaneous	$ 0	$ 1

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Amount of unrealized and realized gain (loss) on investment in debt and equity securities.

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Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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