Note 4 - Stockholders' Equity (Details Textual) - USD ($)			3 Months Ended	6 Months Ended
	Aug. 15, 2017	Feb. 15, 2017	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Preferred Stock, Par or Stated Value Per Share		$ 0.001	$ 0.001	$ 0.001		$ 0.001
Preferred Stock, Shares Outstanding			6,213	6,213		0
Stock Issued During Period, Shares, New Issues					27,971
Stock Issued During Period, Value, New Issues					$ 71,000
Proceeds from Issuance of Common Stock				$ 1,036,000	$ 69,000
Subsequent Event [Member]
Preferred Stock, Shares Outstanding	3,203
Conversion of Series A Convertible Preferred Stock into Common Stock [Member] | Subsequent Event [Member]
Conversion of Stock, Shares Converted	3,846
Conversion of Stock, Shares Issued	3,846,000
Private Placement [Member]
Convertible Preferred Stock Units, Price Per Unit		$ 1,495
Private Placement [Member] | Series A Units [Member]
Gross Proceeds From Issuance Of Units		$ 10,500,000
Non-cash Consideration Received		$ 1,600,000
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right		1
Stock Issued During Period, Shares, New Issues		7,049
Private Placement [Member] | Series A Warrant [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right		1,000
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 1.37
Class of Warrants, May Not Exercise To Extent, Percentage		9.99%
Stifel ATM Program [Member]
Stock Issued During Period, Shares, New Issues			41,231	847,147
Stock Issued During Period, Value, New Issues			$ 48,000	$ 1,082,000
Proceeds from Issuance of Common Stock			$ 46,000	$ 1,036,000