Note 8 - Income Taxes (Details Textual) - USD ($)		3 Months Ended		12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Income Tax Expense (Benefit), Total		$ 22,180,000	$ 5,280,000
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total		81,450,000	$ 19,490,000
Federal Income Tax Expense (Benefit), Continuing Operations, Total		63,000
Effective Income Tax Rate Reconciliation, Deduction, Dividends, Amount		84,000
Income Tax Expense (Benefit), Provision on Marketable Securities		22,360,000
Deferred State and Local Income Tax Expense (Benefit)		$ (159,000)
Effective Income Tax Rate Reconciliation, Percent, Total		27.00%	27.00%	19.00%
Marketable Securities, Unrealized Gain (Loss), Total	$ (0)	$ 81,212,000	$ 19,531,000
Domestic Tax Authority [Member]
Open Tax Year		2017
State and Local Jurisdiction [Member]
Open Tax Year		2016