Quarterly report pursuant to Section 13 or 15(d)

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

v3.21.1
Note 4 - Marketable Securities - Fair Value of Marketable Securities (Details) - Fair Value, Recurring [Member] - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Total marketable securities $ 20,072 $ 20,098
Fair Value, Inputs, Level 1 [Member]    
Total marketable securities
Fair Value, Inputs, Level 2 [Member]    
Total marketable securities 20,072 20,098
Fair Value, Inputs, Level 3 [Member]    
Total marketable securities
US Government Agencies Debt Securities [Member]    
Total marketable securities 6,004 8,924
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]    
Total marketable securities
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]    
Total marketable securities 6,004 8,924
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]    
Total marketable securities
Bank Certificates of Deposit [Member]    
Total marketable securities 245 496
Bank Certificates of Deposit [Member] | Fair Value, Inputs, Level 1 [Member]    
Total marketable securities
Bank Certificates of Deposit [Member] | Fair Value, Inputs, Level 2 [Member]    
Total marketable securities 245 496
Bank Certificates of Deposit [Member] | Fair Value, Inputs, Level 3 [Member]    
Total marketable securities
Commercial Paper and Corporate Bonds [Member]    
Total marketable securities 13,823 10,678
Commercial Paper and Corporate Bonds [Member] | Fair Value, Inputs, Level 1 [Member]    
Total marketable securities
Commercial Paper and Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]    
Total marketable securities 13,823 10,678
Commercial Paper and Corporate Bonds [Member] | Fair Value, Inputs, Level 3 [Member]    
Total marketable securities