Note 1 - Organization and Basis of Presentation (Details Textual) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended	6 Months Ended		11 Months Ended
	Sep. 15, 2021	Oct. 13, 2020	Sep. 30, 2021	Dec. 31, 2020	Jun. 30, 2022	Jun. 30, 2021	Sep. 13, 2021
Proceeds from Issuance of Common Stock					$ 3,797	$ 101,914
The October 2020 Offering [Member]
Open Market Sale Agreement, Maximum Aggregate Offering Price		$ 250,000
Payments of Stock Issuance Costs		$ 300
Open Market Sale Agreement, Sales Commission, Percentage		4.50%
Stock Issued During Period, Shares, New Issues (in shares)				692,651		10,958,908	13,932,490
Proceeds from Issuance of Common Stock				$ 5,500		$ 106,900	$ 133,400
Proceeds from Issuance of Common Stock, Net				$ 4,900		$ 101,900	$ 127,100
The September 2021 ATM [Member]
Open Market Sale Agreement, Maximum Aggregate Offering Price	$ 100,000
Open Market Sale Agreement, Sales Commission, Percentage	3.00%
Stock Issued During Period, Shares, New Issues (in shares)			0		776,000
Proceeds from Issuance of Common Stock					$ 4,200
Proceeds from Issuance of Common Stock, Net					$ 3,800