Note 10 - Equity Incentive Plans - Summary of Stock Option and RSU Transactions (Details) - $ / shares	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Shares available for grant (in shares)	5,582,742
Number of options outstanding (in shares)	10,216,106
Weighted average exercise price (in dollars per share)	$ 4.96
Shares available for grant, granted (in shares)	(5,137,646)
Number of options outstanding, granted (in shares)	4,628,585
Weighted average exercise price, granted (in dollars per share)	$ 4.49
Number of options outstanding, exercised (in shares)	(70,643)	(571,926)
Weighted average exercise price, exercised (in dollars per share)	$ 1.11
Shares available for grant, forfeited (in shares)	430,720
Number of options outstanding, forfeited (in shares)	(429,196)
Weighted average exercise price, forfeited (in dollars per share)	$ 6.72
Canceled (in shares)	28,750
Canceled (in shares)	(38,934)
Canceled (in dollars per share)	$ 10.44
Shares available for grant (in shares)	904,566
Number of options outstanding (in shares)	14,305,918
Weighted average exercise price (in dollars per share)	$ 4.76
Restricted Stock Units (RSUs) [Member]
Number of RSUs outstanding (in shares)	0
Weighted average grant date fair value (in dollars per share)	$ 0
Number of RSUs outstanding, granted (in shares)	509,061
Weighted average grant date fair value, granted (in dollars per share)	$ 3.95
Number of RSUs outstanding, exercised (in shares)	0
Weighted average grant date fair value, exercised (in dollars per share)	$ 0
Number of RSUs outstanding, forfeited (in shares)	(1,589)
Weighted average grant date fair value, forfeited (in dollars per share)	$ 2.89
Number of RSUs outstanding (in shares)	507,472
Weighted average grant date fair value (in dollars per share)	$ 3.95