Note 8 - Preferred Stock (Details Textual) - $ / shares	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2017	Oct. 17, 2017	Dec. 31, 2016	Dec. 31, 2004
Preferred Stock, Shares Authorized	0	5,000,000				5,000,000
Preferred Stock, Shares Outstanding, Ending Balance					0
Series B Preferred Stock [Member]
Preferred Stock, Shares Authorized				50,000
Preferred Stock, Shares Outstanding, Ending Balance	0	15,500
Preferred Stock, Shares Issued, Total	0	15,500		35,600
Convertible Preferred Stock, Shares Issued upon Conversion			400
Preferred Stock, Liquidation Preference Per Share			$ 100