Note 13 - Commitments and Contingencies (Details Textual) $ / shares in Units, $ in Millions		12 Months Ended
	Apr. 30, 2023 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares	Dec. 31, 2022 USD ($) $ / shares	Sep. 20, 2022 USD ($)	May 31, 2019 a	Jul. 31, 2017 a
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares		$ 0.001	$ 0.001
Operating Lease, Expense		$ 2.3	$ 2.1
Corporate Headquarters in Hayward, California [Member]
Lessee, Operating Lease, Term of Contract (Year)						5 years
Area of Real Estate Property (Acre) | a						15,700
Corporate Headquarters in Hayward, California [Member] | Expansion Premises 1 [Member]
Area of Real Estate Property (Acre) | a					13,300
Corporate Headquarters in Hayward, California [Member] | Expansion Premises 2 [Member]
Area of Real Estate Property (Acre) | a					21,300
Robert W. Duggan [Member] | Private Placement [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares	10,022,937
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares	$ 0.001
Shares Issued, Price Per Share (in dollars per share) | $ / shares	$ 6.51
Two Thousand Twenty Two Loan Agreement [Member] | Robert W. Duggan [Member]
Debt Instrument, Face Amount				$ 65.0
Debt Instrument Quarterly Interest Rate				5
Debt Instrument, Increase, Accrued Interest		1.7
Interest Expense		$ 1.1
Loan Agreement [Member]
Debt Instrument, Decrease, Forgiveness	$ 65.0
Interest Payable	$ 0.2