Note 10 - Convertible Preferred Stock Warrant Liability (Details Textual) - USD ($)		12 Months Ended
	Oct. 24, 2016	Dec. 31, 2016
Stock Issued During Period, Value, Exchange of Convertible Preferred Stock Warrants to Common Stock	$ 25,000	$ 25,000
Warrant to Purchase Series D Convertible Preferred Stock [Member]
Exchange of Convertible Preferred Stock Warrants for Common Stock, Percentage	20.00%
Stock Issued During Period, Shares, Exchange of Convertible Preferred Stock Warrants to Common Stock	6,788
Warrant to Purchase Series F Convertible Preferred Stock [Member]
Exchange of Convertible Preferred Stock Warrants for Common Stock, Percentage	10.00%
Stock Issued During Period, Shares, Exchange of Convertible Preferred Stock Warrants to Common Stock	4,019