Note 2 - Significant Accounting Policies - Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Losses on available-for-sale marketable securities		$ 1,654	$ 1,815	$ 1,669
Net loss		(1,190)	(1,957)	(3,003)
Research and development	[1]	35,552	36,109	36,655
Sales and marketing	[2]	17,665	15,323	14,315
General and administrative	[3]	10,317	9,955	9,789
Research and development	[1]	35,552	36,109	36,655
Sales and marketing	[2]	17,665	$ 15,323	$ 14,315
Reclassification out of Accumulated Other Comprehensive Income [Member]
Net loss		(16)
Reclassification out of Accumulated Other Comprehensive Income [Member] | AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Losses on available-for-sale marketable securities		73
Net loss		73
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Net loss		(105)
Research and development		(83)
Sales and marketing		(8)
General and administrative		(14)
Research and development		(83)
Sales and marketing		(8)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Net loss		16
Research and development		11
Sales and marketing		5
General and administrative		16
Research and development		11
Sales and marketing		$ 5

[1] Includes equity-based compensation expense in the amount of $2,842, $2,873 and $2,349 for the years ended December 31, 2019, 2018 and 2017, respectively.

[2] Includes equity-based compensation expense in the amount of $1,758, $1,248 and $1,115 for the years ended December 31, 2019, 2018 and 2017, respectively.

[3] Includes equity-based compensation expense in the amount of $2,583, $2,255 and $2,045 for the years ended December 31, 2019, 2018 and 2017, respectively.