Note 10 - Investments in Marketable Securities (Details Textual)	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Equity Securities Fv Ni Gross Unrealized Gain	$ 77,991,000		$ 77,991,000		$ 85,394,000
Equity Securities Fv Ni Gross Unrealized Loss	5,022,000		5,022,000		946,000
Equity Securities, FV-NI, Unrealized Gain (Loss), Total	(11,056,000)	$ (23,797,000)	(11,479,000)	$ (23,227,000)
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax	0		0		3,189,000
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	$ 12,099,000		$ 12,099,000		$ 1,176,000
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions	52		52
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 45,367,000		$ 45,367,000
Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale, Total			0	0
Proceeds from Sale and Maturity of Marketable Securities			38,114,000	89,129,000
Debt Securities, Realized Gain (Loss), Total			$ (756,000)	$ 941,000