Note 4 - Common Stock - Changes in Common Stock Issued and Outstanding (Details) (Parentheticals) - $ / shares	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Common stock, par value (in dollars per share)	$ 0.50	$ 0.50	$ 0.50
Common stock, shares authorized (in shares)	200,000	200,000	200,000