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Note J - Fair Value of Financial Instruments - Securities Measured at Fair Value on a Recurring Basis (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Marketable equity securities $ 31,913 $ 27,941
Fair Value, Inputs, Level 1 [Member]    
Marketable equity securities 31,913  
Fair Value, Inputs, Level 2 [Member]    
Marketable equity securities 0  
Fair Value, Inputs, Level 3 [Member]    
Marketable equity securities $ 0