Note 7 - Stockholders' Equity, Stock Plans and Stock-based Compensation Expense - Activity Pursuant to the Amended and Restated Plans (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock options (in shares)	77,511	413,588	447,673	706,522
Stock awards, net of shares withheld to satisfy employees’ minimum income tax withholding (in shares)	9,881	8,107	152,972	114,832
ESPP (in shares)			51,185	41,980
Total stock issued (in shares)	87,392	421,695	651,830	863,334