Note 2 - Net Loss Per Common Share (Tables)

9 Months Ended

Sep. 30, 2020

Notes Tables

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Shares of common stock subject to outstanding options		4,492,414		5,299,296		4,691,424		5,562,611
Employee stock purchase plan		15,673		51,253		20,151		32,272
Restricted stock units		891,087		780,914		929,968		691,647
Total common stock equivalents		5,399,174		6,131,463		5,641,543		6,286,530