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, 2022	Dec. 31, 2021
Financial Assets
Cash	$ 35,311	$ 37,168
Accrued interest and dividends	872	817
Common stocks	51,691	76,853
Money market funds and US treasury bills	103,649	45,930
Equity investments in unconsolidated affiliates, measurement alternative	8,915	8,688
Assets, Fair Value Disclosure	200,438	169,456
Level 1
Financial Assets
Cash	35,311	37,168
Accrued interest and dividends	872	817
Common stocks	51,691	76,853
Money market funds and US treasury bills	103,649	45,930
Equity investments in unconsolidated affiliates, measurement alternative	0	0
Assets, Fair Value Disclosure	191,523	160,768
Level 2
Financial Assets
Cash	0	0
Accrued interest and dividends	0	0
Common stocks	0	0
Money market funds and US treasury bills	0	0
Equity investments in unconsolidated affiliates, measurement alternative	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 US treasury bills	0	0
Equity investments in unconsolidated affiliates, measurement alternative	8,915	8,688
Assets, Fair Value Disclosure	$ 8,915	$ 8,688