Note 6 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Feb. 18, 2021
Subsidiary or Equity Method Investee [Line Items]
Share-Based Payment Arrangement, Expense	$ 1,200	$ 1,200
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 5,200
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	1 year 3 months 18 days
Share-Based Payment Arrangement, Shares Withheld for Tax Withholding Obligation (in shares)	277,966
Share-Based Payment Arrangement, Decrease for Tax Withholding Obligation	$ 1,200
Shares Withheld for Tax Withholding Obligation, Price Per Share (in dollars per share)	$ 4.31
Equity Distribution Agreement, Maximum Number of Shares to be Sold (in shares)	14,753,958
Proceeds from Issuance or Sale of Equity	$ 1,100
Payments of Stock Issuance Costs	$ 40
Common stock issued under ATM program, net shares	248,561	2,173,274,000
At the market Offering [Member]
Subsidiary or Equity Method Investee [Line Items]
Equity Distribution Agreement, Maximum Number of Shares to be Sold (in shares)			60,000,000
At the market Offering [Member] | At The Market Equity Distribution Agreement [Member]
Subsidiary or Equity Method Investee [Line Items]
Proceeds from Issuance or Sale of Equity	$ 76,700
Payments of Stock Issuance Costs	$ 1,200