Note 6 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Feb. 18, 2021
Subsidiary or Equity Method Investee [Line Items]
Share-Based Payment Arrangement, Expense	$ 2,300	$ 2,400	$ 6,400	$ 5,100
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 10,000		$ 10,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			2 years 2 months 12 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		$ 4.31
Equity Distribution Agreement, Maximum Number of Shares to be Sold (in shares)	23,844,684,000		23,844,684,000
Proceeds from Issuance or Sale of Equity	$ 57,300		$ 58,400
Payments of Stock Issuance Costs			$ 940
Common stock issued under ATM program, net shares	9,090,726	125,063	9,339,287	4,253,334
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			$ 132,300
Payments of Stock Issuance Costs	$ 900		$ 2,100