Note 6 - Fair Value Measurement - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Marketable securities	$ 67,293	$ 64,867
Foreign exchange contracts	251	56
Fair Value, Inputs, Level 1 [Member]
Foreign exchange contracts	0	0
Fair Value, Inputs, Level 2 [Member]
Foreign exchange contracts	251	56
Fair Value, Inputs, Level 3 [Member]
Foreign exchange contracts	0
Corporate Bonds [Member]
Marketable securities	67,293	64,867
Corporate Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities	0	0
Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities	67,293	64,867
Corporate Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable securities	$ 0	$ 0