Note 6 - Fair Value Measurement - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Marketable securities	$ 67,909	$ 64,867
Foreign exchange contracts	271	56
Foreign exchange contracts	14
Fair Value, Inputs, Level 1 [Member]
Foreign exchange contracts
Foreign exchange contracts
Fair Value, Inputs, Level 2 [Member]
Foreign exchange contracts	271	56
Foreign exchange contracts	14
Fair Value, Inputs, Level 3 [Member]
Foreign exchange contracts
Foreign exchange contracts
Corporate Bonds [Member]
Marketable securities	67,909	64,867
Corporate Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities
Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities	67,909	64,867
Corporate Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable securities