Note 3 - Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Total	$ 33,801	$ 64,465
Foreign currency forward contracts		537
Total		537
Cash Equivalents [Member]
Cash equivalents	28,876	39,233
US Government Agencies Debt Securities [Member]
Government securities	4,925	25,232
Fair Value, Inputs, Level 1 [Member]
Total	33,801	64,465
Foreign currency forward contracts
Total
Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member]
Cash equivalents	28,876	39,233
Fair Value, Inputs, Level 1 [Member] | US Government Agencies Debt Securities [Member]
Government securities	4,925	25,232
Fair Value, Inputs, Level 2 [Member]
Total
Foreign currency forward contracts		537
Total		537
Fair Value, Inputs, Level 2 [Member] | Cash Equivalents [Member]
Cash equivalents
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Government securities
Fair Value, Inputs, Level 3 [Member]
Total
Foreign currency forward contracts
Total
Fair Value, Inputs, Level 3 [Member] | Cash Equivalents [Member]
Cash equivalents
Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member]
Government securities