Note 11 - Warrant Liability (Details Textual) - USD ($)					1 Months Ended			3 Months Ended			12 Months Ended
	Aug. 08, 2019	Oct. 27, 2015	Oct. 22, 2015	Mar. 03, 2015	Jul. 31, 2019	Oct. 31, 2015	Jul. 31, 2011	Sep. 30, 2019	Jun. 30, 2019	Jun. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 09, 2019	Aug. 31, 2019	Aug. 13, 2019	May 31, 2019	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2016	Feb. 29, 2016	Mar. 31, 2015	Jan. 05, 2012
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Warrants Issued							139,520
Class of Warrant or Right, Exercise Price of Warrants or Rights							$ 33.25				$ 1.09	$ 1.81	$ 1.81							$ 1.81
Minimum Common Stock Closing Bid Price Per Share																							$ 66.50
Stock Issued During Period, Shares, New Issues	4,198,566							4,198,566
Shares Issued, Price Per Share	$ 1	$ 5
Additional Paid in Capital, Ending Balance											$ 125,718,000	$ 119,764,000
Class of Warrant or Right, Exercised During Period											394,000		21,000
Proceeds from Warrant Exercises											$ 67,000		$ 38,000
Embedded Derivative, No Longer Bifurcated, Amount Reclassified to Stockholders' Equity											553,000		$ 58,000
Accounting Standards Update 2017-11 [Member]
Warrants and Rights Outstanding											(56,000)							$ (56,000)	$ (56,000)
Additional Paid in Capital, Ending Balance											56,000							$ 56,000	356,000
Accounting Standards Update 2017-11 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption																			$ (356,000)
Underwriting Agreement [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 5
Warrants and Rights Outstanding, Term		5 years
Stock Issued During Period, Shares, New Issues		492,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights		442,802
Proceeds from Issuance of Stock and Warrants		$ 2,100,000
Warrants and Rights Outstanding		1,300,000
March 2015 Short-term and Long-term Warrants [Member]
Length of Notice for warrant Holders				20 days		2 days
Class of Warrant or Right, Number of Securities Called by Warrants or Rights									133,167	21,000
Class of Warrant or Right, Exercised During Period									133,167	21,000
Proceeds from Warrant Exercises									$ 13,000	$ 38,000
Warrant Liabilities, Fair Value Disclosure										58,000
Fair Market Value of Warrants Transferred to Equity Upon Exercise										$ 58,000
Short-term Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights																						$ 15
Short-term Warrants [Member] | Private Placement [Member]
Warrants and Rights Outstanding, Term			1 year 90 days
Long-term Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights																						$ 16.25
Long-term Warrants [Member] | Private Placement [Member]
Warrants and Rights Outstanding, Term			5 years
The 2011 and March 2015 Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights			$ 5
Class of Warrant or Right Price Protection Provision Exchangeable Securities Exercise Price Trigger			$ 5
Warrants and Rights Outstanding		$ 1,800,000
July 2011, March 2015, and October 2015 Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights																	$ 0.2061				$ 1.81
July 2011 and October 2015 Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights					102,602			102,602	158,400
Warrants and Rights Outstanding								$ 200,000	$ 400,000
Class of Warrant or Right, Exercised During Period					102,602			102,602	158,400
Proceeds from Warrant Exercises					$ 21,000			$ 21,000	$ 33,000
Embedded Derivative, No Longer Bifurcated, Amount Reclassified to Stockholders' Equity								$ 200,000	$ 400,000
The 2019 Domestic Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 1.15														$ 1.15	$ 1.15
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	4,198,566														4,198,566
Warrants and Rights Outstanding	$ 3,100,000										2,410,000					$ 3,100,000
Additional Paid in Capital, Ending Balance	$ (255,000)
The 2019 Foreign Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights														$ 1.15	$ 1.15
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	2,700,000													2,700,000	2,700,000
Warrants and Rights Outstanding	$ 2,000,000										1,550,000					$ 2,000,000
The 2019 Ladenburg Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 1.25														$ 1.25	$ 1.25
Class of Warrant or Right, Number of Securities Called by Warrants or Rights															167,942
Warrants and Rights Outstanding											$ 95,000					$ 124,000