Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accounts receivable, allowance for doubtful accounts	$ 20	$ 18
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	51,820,425	51,589,674
Common stock, shares outstanding (in shares)	51,820,425	51,589,674
Series G Preferred Stock [Member]
Preferred stock, shares authorized (in shares)	3,000	3,000
Preferred stock, stated value (in dollars per share)	$ 150	$ 150
Preferred stock, shares issued (in shares)	150	150
Preferred stock, shares outstanding (in shares)	150	150