Investments (Major Categories of Net Investment Gains (Losses) on Investments) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Gain (Loss) on Securities [Line Items]
Gain on investments	$ 1,403	$ 5,636
Investment gains (losses), net	5,779	(29,330)
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on equity securities	1,164	4,309
Unrealized gain (losses)	4,376	(32,965)
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Unrealized gain (losses)	0	(2,001)
Corporate Bonds [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on debt securities	197	55
Corporate bank loans [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on debt securities	51	(148)
Municipal Bonds [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on debt securities	$ (9)	$ 1,420

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

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

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Amount of realized gain (loss) 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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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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