Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.1
Note 4 - Marketable Securities - Fair Value of Marketable Securities (Details) - Fair Value, Recurring [Member]
$ in Thousands
Mar. 31, 2019
USD ($)
Commercial paper and corporate bonds $ 10,958
Fair Value, Inputs, Level 1 [Member]  
Commercial paper and corporate bonds
Fair Value, Inputs, Level 2 [Member]  
Commercial paper and corporate bonds 10,958
Fair Value, Inputs, Level 3 [Member]  
Commercial paper and corporate bonds
Commercial Paper and Corporate Bonds [Member]  
Commercial paper and corporate bonds 3,978
Commercial Paper and Corporate Bonds [Member] | Fair Value, Inputs, Level 1 [Member]  
Commercial paper and corporate bonds
Commercial Paper and Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]  
Commercial paper and corporate bonds 3,978
Commercial Paper and Corporate Bonds [Member] | Fair Value, Inputs, Level 3 [Member]  
Commercial paper and corporate bonds
US Government Agencies Debt Securities [Member]  
Commercial paper and corporate bonds 6,980
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]  
Commercial paper and corporate bonds
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]  
Commercial paper and corporate bonds 6,980
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]  
Commercial paper and corporate bonds