Note 11 - Financing Transactions (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Mar. 18, 2022
Proceeds from Issuance of Common Stock, Net		$ 0	$ 129,322
Proceeds from Warrant Exercises			$ 30,500
Public Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)	26,545,832
Shares Issued, Price Per Share (in dollars per share)	$ 3.00
Proceeds from Issuance of Common Stock, Net	$ 73,400
Registered Direct Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)	25,000,000
Shares Issued, Price Per Share (in dollars per share)	$ 1.25
Proceeds from Issuance of Common Stock	$ 28,600
The 2022 Sales Agreement [Member]
Stock Issued During Period, Shares, New Issues (in shares)		0
Equity Offering Agreement, Amount Issuable				$ 100,000