Note 10 - Investments in Marketable Securities (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Equity Securities Fv Ni Gross Unrealized Gain	$ 73,823,000		$ 73,823,000		$ 71,869,000
Equity Securities Fv Ni Gross Unrealized Loss	2,238,000		2,238,000		3,227,000
Equity Securities, FV-NI, Unrealized Gain (Loss)	(3,093,000)	$ (11,056,000)	2,943,000	$ (11,479,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax	3,000		3,000		9,000
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	11,651,000		11,651,000		11,071,000
Debt Securities, Available-for-Sale, Unrealized Loss Position	$ 123,530,000		123,530,000		$ 139,629,000
Other-than-temporary Impairment Loss, Debt Securities, Available-for-Sale			0	0
Proceeds from Sale and Maturity of Marketable Securities			36,578,000	38,114,000
Debt Securities, Realized Gain (Loss)			$ (603,000)	$ (756,000)