Note 1 - General - Cash, Cash Equivalents and Short-term Investments (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Member]
Gross unrealized gains
Gross unrealized losses
Fair value		53,539	48,315
Amortized Cost		53,539	48,315
Cash and Cash Equivalents [Member] | Cash [Member]
Gross unrealized gains
Gross unrealized losses
Fair value		40,083	42,175
Amortized Cost		40,083	42,175
Cash and Cash Equivalents [Member] | Money Market Funds [Member]
Gross unrealized gains
Gross unrealized losses
Fair value		12,456	6,140
Amortized Cost		12,456	6,140
Cash and Cash Equivalents [Member] | US Treasury Securities Included in Cash and Cash Equivalents [Member]
Gross unrealized gains
Gross unrealized losses	[1]
Fair value		1,000
Amortized Cost		1,000
Short-term Investments [Member]
Gross unrealized gains
Gross unrealized losses		(10)
Fair value		68,039	65,493
Amortized Cost		68,049	65,493
Short-term Investments [Member] | Term Bank Deposits [Member]
Gross unrealized gains
Gross unrealized losses
Fair value		35,103	65,493
Amortized Cost		35,103	$ 65,493
Short-term Investments [Member] | US Treasury Securities [Member]
Gross unrealized gains
Gross unrealized losses		(10)
Fair value		32,936
Amortized Cost		$ 32,946

[1] Represents an amount lower than $ 1.