Note 6 - Fair Value Measurement - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Marketable securities		$ 77,587	$ 77,469
Foreign exchange contracts		56
Investment in other company	[1]		936
Foreign exchange contracts			77
Fair Value, Inputs, Level 1 [Member]
Foreign exchange contracts
Investment in other company	[1]
Foreign exchange contracts
Fair Value, Inputs, Level 2 [Member]
Foreign exchange contracts		56
Investment in other company	[1]
Foreign exchange contracts			77
Fair Value, Inputs, Level 3 [Member]
Foreign exchange contracts
Investment in other company	[1]		936
Foreign exchange contracts
Certificates of Deposits [Member]
Marketable securities		747	747
Certificates of Deposits [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities
Certificates of Deposits [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities		747	747
Certificates of Deposits [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable securities
Government Bonds [Member]
Marketable securities		498	496
Government Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities
Government Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities		498	496
Government Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable securities
Corporate Bonds [Member]
Marketable securities		76,342	76,226
Corporate Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities
Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities		76,342	76,226
Corporate Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable securities

[1] Non- marketable equity securities remeasured during the year ended December 31, 2018.