Note 2 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Total financial assets (liabilities)	$ 71,633
Foreign Exchange Forward [Member]
Derivative Assets
Derivative Liabilities
Cash and Cash Equivalents [Member] | Money Market Funds [Member]
Cash equivalents	6,140
Cash and Cash Equivalents [Member] | US Treasury Securities Included in Cash and Cash Equivalents [Member]
Cash equivalents
Short-term Investments [Member] | US Treasury Securities [Member]
Short-term investments
Short-term Investments [Member] | Term Bank Deposits [Member]
Short-term investments	65,493
Fair Value, Inputs, Level 1 [Member]
Total financial assets (liabilities)	81,495	$ (479)
Fair Value, Inputs, Level 1 [Member] | Foreign Exchange Forward [Member]
Derivative Assets
Derivative Liabilities		(479)
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member] | Money Market Funds [Member]
Cash equivalents	12,456
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member] | US Treasury Securities Included in Cash and Cash Equivalents [Member]
Cash equivalents	1,000
Fair Value, Inputs, Level 1 [Member] | Short-term Investments [Member] | US Treasury Securities [Member]
Short-term investments	32,936
Fair Value, Inputs, Level 1 [Member] | Short-term Investments [Member] | Term Bank Deposits [Member]
Short-term investments	35,103
Fair Value, Inputs, Level 2 [Member]
Total financial assets (liabilities)	2,138	71,154
Fair Value, Inputs, Level 2 [Member] | Foreign Exchange Forward [Member]
Derivative Assets	2,138
Derivative Liabilities		(479)
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member] | Money Market Funds [Member]
Cash equivalents		6,140
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member] | US Treasury Securities Included in Cash and Cash Equivalents [Member]
Cash equivalents
Fair Value, Inputs, Level 2 [Member] | Short-term Investments [Member] | US Treasury Securities [Member]
Short-term investments
Fair Value, Inputs, Level 2 [Member] | Short-term Investments [Member] | Term Bank Deposits [Member]
Short-term investments		$ 65,493
Fair Value, Inputs, Level 3 [Member]
Total financial assets (liabilities)	83,633
Fair Value, Inputs, Level 3 [Member] | Foreign Exchange Forward [Member]
Derivative Assets	2,138
Derivative Liabilities
Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member] | Money Market Funds [Member]
Cash equivalents	12,456
Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member] | US Treasury Securities Included in Cash and Cash Equivalents [Member]
Cash equivalents	1,000
Fair Value, Inputs, Level 3 [Member] | Short-term Investments [Member] | US Treasury Securities [Member]
Short-term investments	32,936
Fair Value, Inputs, Level 3 [Member] | Short-term Investments [Member] | Term Bank Deposits [Member]
Short-term investments	$ 35,103