Quarterly report pursuant to Section 13 or 15(d)

Note 4 - Marketable Securities - Fair Value of Marketable Securities (Details)

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Note 4 - Marketable Securities - Fair Value of Marketable Securities (Details) - USD ($)
$ in Thousands
Mar. 31, 2023
Dec. 31, 2022
Total marketable securities $ 0 $ 0
Fair Value, Recurring [Member]    
Total marketable securities 26,508 28,774
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]    
Total marketable securities 26,508 28,774
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Total marketable securities 0 0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]    
Total marketable securities 0 0
Fair Value, Recurring [Member] | Commercial Paper and Corporate Bonds [Member]    
Total marketable securities 12,892 14,209
Fair Value, Recurring [Member] | Commercial Paper and Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]    
Total marketable securities 12,892 14,209
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]    
Total marketable securities 13,616 14,565
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]    
Total marketable securities 13,616 14,565
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]    
Total marketable securities 0 0
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]    
Total marketable securities $ 0 $ 0