Note 1 - Nature of Business and Significant Accounting Policies (Details Textual) $ / shares in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) a $ / shares	Dec. 31, 2019 USD ($) $ / shares
Equity Securities, FV-NI	$ 502,595	$ 500,642
Accounts Receivable, Allowance for Credit Loss, Current	0
Impairment of Long-Lived Assets Held-for-use	0	0
Accrued Royalty Income	49,113	84,880
Deposit Assets, Stumpage Agreements	$ 87,300	$ 87,300
Earnings Per Share, Diluted, Total (in dollars per share) | $ / shares	$ 0	$ 0
Payments of Ordinary Dividends, Common Stock	$ 0	$ 0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	0
Taxes, Other	125,124	151,204
Oil and Gas [Member]
Capitalized Contract Cost, Net, Total	$ 0
Southwest Louisiana [Member]
Area of Land (Acre) | a	13,941
Southwest Louisiana [Member] | Timber Properties [Member]
Area of Land (Acre) | a	10,495
Mutual Fund [Member]
Equity Securities, FV-NI	$ 502,595	$ 500,642