Note 11 - Stock-based Compensation - Stock Options Outstanding (Details) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($) $ / shares shares
Options, Exercisable, Number of Shares (in shares) | shares	3,119,355
Options, Exercisable, Weighted Average Exercise Price (in dollars per share) | $ / shares (in dollars per share) | $ / shares	$ 8.02
Options, Exercisable, Weighted Average Remaining Contractual Term (Year)	5 years 29 days
Options, Exercisable, Aggregate Intrinsic Value | $	$ 0
Options, Vested and Expected to Vest, Exercisable, Number of Shares (in shares) | shares	6,777,170
Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 4.67
Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term (Year)	5 years 8 months 1 day
Options, Vested or Expected to Vest, Aggregate Intrinsic Value | $	$ 0