Note J - Fair Value of Financial Instruments - Securities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Marketable equity securities	$ 29,454	$ 27,549
Fair Value, Inputs, Level 1 [Member]
Marketable equity securities	29,454
Fair Value, Inputs, Level 2 [Member]
Marketable equity securities	0
Fair Value, Inputs, Level 3 [Member]
Marketable equity securities	$ 0