Note J - Fair Value of Financial Instruments - Securities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Marketable equity securities	$ 25,157	$ 29,521
Fair Value, Inputs, Level 1 [Member]
Marketable equity securities	25,157
Fair Value, Inputs, Level 2 [Member]
Marketable equity securities	0
Fair Value, Inputs, Level 3 [Member]
Marketable equity securities	$ 0