Investments in Securities and Fair Value (Schedule of Carrying Value and Fair Value of Financial Assets Disclosed) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 37,310	$ 37,168
Accrued interest and dividends	1,000	817
Equity securities, estimated fair value	69,945	76,853
Money market funds	58,555	45,930
Equity investments in unconsolidated affiliates, measurement alternative	8,908	8,688
Assets, fair value disclosure	175,718	169,456
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	37,310	37,168
Accrued interest and dividends	1,000	817
Equity securities, estimated fair value	69,945	76,853
Money market funds	58,555	45,930
Equity investments in unconsolidated affiliates, measurement alternative	0	0
Assets, fair value disclosure	166,810	160,768
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Accrued interest and dividends	0	0
Equity securities, estimated fair value	0	0
Money market funds	0	0
Equity investments in unconsolidated affiliates, measurement alternative	0	0
Assets, fair value disclosure	0	0
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Accrued interest and dividends	0	0
Equity securities, estimated fair value	0	0
Money market funds	0	0
Equity investments in unconsolidated affiliates, measurement alternative	8,908	8,688
Assets, fair value disclosure	$ 8,908	$ 8,688