Note 2 - Significant Accounting Policies - Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Losses on available-for-sale marketable securities		$ 1,815	$ 1,669	$ 1,227
Net income		(1,957)	(3,003)	4,813
Research and development	[1]	36,109	36,655	34,885
Sales and marketing	[2]	15,323	14,315	13,867
General and administrative	[3]	9,955	9,789	9,006
Research and development	[1]	36,109	36,655	34,885
Sales and marketing	[2]	15,323	$ 14,315	$ 13,867
Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income		76
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Losses on available-for-sale marketable securities		41
Net income		41
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Net income		16
Research and development		13
Sales and marketing		1
General and administrative		2
Research and development		13
Sales and marketing		1
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Net income		19
Research and development		12
Sales and marketing		7
General and administrative		19
Research and development		12
Sales and marketing		$ 7

[1] Includes equity-based compensation expense in the amount of $2,873, $2,349 and $2,205 for the years ended December 31, 2018, 2017 and 2016, respectively.

[2] Includes equity-based compensation expense in the amount of $1,248, $1,115 and $806 for the years ended December 31, 2018, 2017 and 2016, respectively.

[3] Includes equity-based compensation expense in the amount of $2,255, $2,045 and $1,749 for the years ended December 31, 2018, 2017 and 2016, respectively.