Note 6 - Series A Preferred Financing (Details Textual) - USD ($)		3 Months Ended		9 Months Ended
	Aug. 02, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Preferred Stock, Par or Stated Value Per Share		$ 0.001		$ 0.001		$ 0.001
Proceeds from Issuance of Convertible Preferred Stock				$ 21,536,000
Accretion of Redeemable Convertible Preferred Stock to Redemption Value		$ 6,747,000	$ 0	$ 6,747,000	$ 0
Series A Convertible Preferred Stock [Member]
Preferred Stock, Par or Stated Value Per Share	$ 0.001	$ 0.001		$ 0.001		$ 0.001
Shares Issued, Price Per Share	$ 1,000
Proceeds from Issuance of Convertible Preferred Stock	$ 22,000,000
Payments of Stock Issuance Costs	$ 500,000
Convertible Preferred Stock, Shares Issued upon Conversion	1,005
Convertible Preferred Stock, Conversion Price of Shares Issued upon Conversion	$ 0.9949
Convertible Preferred Stock, Maximum Ownership Percentage Allowed after Conversion of Stock	9.985%
Preferred Stock, Redemption Price Per Share	$ 1.30
Accretion of Redeemable Convertible Preferred Stock to Redemption Value	$ 6,700,000
Stock Issued During Period, Shares, New Issues	22,000