Note 11 - Stock-based Compensation (Details Textual) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) $ / shares
Share-based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit (in dollars per share) | $ / shares	$ 20
Share-based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit (in dollars per share) | $ / shares	$ 99,300
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value | $	$ 0
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | $	$ 1,900
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	1 year 36 days