Note 20 - Subsequent Events (Details Textual) - USD ($)		2 Months Ended	3 Months Ended	12 Months Ended
	Mar. 20, 2019	Feb. 25, 2021	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Issued During Period, Shares, New Issues (in shares)	1,200,000
Proceeds from Issuance of Common Stock	$ 2,500,000
Proceeds from Warrant Exercises				$ 25,951,000	$ 180,000
Subsequent Event [Member] | Warrants Issued in Connection with Open Market Sale Agreement [Member]
Class of Warrant or Right, Exercised During Period (in shares)		830,722
Proceeds from Warrant Exercises		$ 1,600,000
Open Market Sale Agreement [Member]
Stock Issued During Period, Shares, New Issues (in shares)			692,651
Proceeds from Issuance of Common Stock			$ 4,900,000
Open Market Sale Agreement [Member] | Subsequent Event [Member]
Stock Issued During Period, Shares, New Issues (in shares)		6,654,367
Proceeds from Issuance of Common Stock		$ 65,800,000