Investments in Securities and Fair Value Investments in Securities (Schedule of Carrying Value and Fair Value of Financial Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financial Assets
Cash	$ 24,031	$ 35,311
Accrued interest and dividends	978	872
Common stocks	37,212	51,691
Money market funds and U.S. Treasury bills	110,224	103,649
Assets, Fair Value Disclosure	172,445	191,523
Level 1
Financial Assets
Cash	24,031	35,311
Accrued interest and dividends	978	872
Common stocks	37,212	51,691
Money market funds and U.S. Treasury bills	110,224	103,649
Assets, Fair Value Disclosure	172,445	191,523
Level 2
Financial Assets
Cash	0	0
Accrued interest and dividends	0	0
Common stocks	0	0
Money market funds and U.S. Treasury bills	0	0
Assets, Fair Value Disclosure	0	0
Level 3
Financial Assets
Cash	0	0
Accrued interest and dividends	0	0
Common stocks	0	0
Money market funds and U.S. Treasury bills	0	0
Assets, Fair Value Disclosure	$ 0	$ 0