Note J - Fair Value of Financial Instruments - Securities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Marketable equity securities	$ 26,104	$ 26,664
Fair Value, Inputs, Level 1 [Member]
Marketable equity securities	26,104
Fair Value, Inputs, Level 2 [Member]
Marketable equity securities	0
Fair Value, Inputs, Level 3 [Member]
Marketable equity securities	$ 0