Investments in Securities and Fair Value Investments in Securities (Schedule of Gross Realized Gains and Losses on Securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Debt and equity securities, realized gains	$ 16,350	$ 11,020
Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale, Recognized in Earnings	(201)	(172)
Debt and equity securities, realized losses	(601)	(919)
Debt and equity securities, net realized gain (loss)	15,749	10,101
Gains on other assets and investments	5	0
Losses on other assets and investments	(123)	(366)
Net gains (losses) on sales of other investments	(118)	(366)
Net realized investment gains (losses)	15,631	9,735
Unrealized Gain (Loss) on Investments	(12,183)	(20,961)
Net investment gains (losses)	3,448	(11,226)
General obligations of U.S. states, territories and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Debt securities, realized losses	0	(353)
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, realized gains	0	0
Debt securities, realized losses	0	(104)
Common stocks and nonredeemable preferred stocks
Debt Securities, Available-for-sale [Line Items]
Equity securities, realized gains	16,350	11,020
Equity Securities, FV-NI, Realized Loss	$ (400)	$ (290)

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