Note 8 - Stock-based Compensation - Stock Option Activity (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($) $ / shares shares
Balance (in shares) | shares	140,040
Balance (in dollars per share) | $ / shares	$ 126.75
Granted (in shares) | shares	0
Granted (in dollars per share) | $ / shares	$ 0
Cancelled (in shares) | shares	(35,993)
Cancelled (in dollars per share) | $ / shares	$ 20.13
Balance (in shares) | shares	104,047
Balance (in dollars per share) | $ / shares	$ 163.64
Outstanding at March 31, 2023 (Year)	7 years 11 months 26 days
Outstanding at March 31, 2023 | $	$ 0
Exercisable at March 31, 2023 (in shares) | shares	78,533
Exercisable at March 31, 2023 (in dollars per share) | $ / shares	$ 211.21
Exercisable at March 31, 2023 (Year)	7 years 9 months
Exercisable at March 31, 2023 | $	$ 0
Vested and expected to vest at March 31, 2023 (in shares) | shares	104,047
Vested and expected to vest at March 31, 2023 (in dollars per share) | $ / shares	$ 163.64
Vested and expected to vest at March 31, 2023 (Year)	7 years 11 months 26 days
Vested and expected to vest at March 31, 2023 | $	$ 0