Note 14 - Equity Offerings (Details Textual) - USD ($)			12 Months Ended
	Jan. 29, 2021	Jan. 12, 2021	Dec. 31, 2022	Dec. 31, 2021	Mar. 18, 2022	May 19, 2021	Oct. 09, 2020
Proceeds from Issuance of Common Stock, Net			$ 0	$ 131,929,000
Proceeds from Warrant Exercises				$ 30,600,000
The 2020 ATM Offering [Member]
Stock Offering Agreement, Maximum Share Value							$ 40,000,000.0
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	$ 73,400,000
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, Net		$ 28,600,000
The 2021 ATM Offering [Member]
Stock Offering Agreement, Maximum Share Value						$ 100,000,000
The 2022 ATM Offering [Member]
Stock Offering Agreement, Maximum Share Value					$ 100,000,000.0
Stock Issued During Period, Shares, New Issues (in shares)			0