Note 16 - Subsequent Events (Details Textual) - USD ($)			9 Months Ended	28 Months Ended	55 Months Ended
	Oct. 27, 2017	Oct. 04, 2017	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2017	Jun. 26, 2017	Jun. 09, 2017	Dec. 31, 2016
Class of Warrant or Right, Exercise Price of Warrants or Rights			$ 5.33	$ 5.33	$ 5.33	$ 1.65	$ 2.70	$ 9.39
Class of Warrant or Right, Issued During Period			6,679,378
Proceeds from Warrant Exercises				$ 800,000	$ 2,100,000
Common Stock, Par or Stated Value Per Share			$ 0.01	$ 0.01	$ 0.01			$ 0.01
Class of Warrant or Right, Number of Securities Called by Warrants or Rights						506,627	790,410
Subsequent Event [Member] | October 2017 Exercise Agreements [Member]
Proceeds from Warrant Exercises		$ 17,000,000
Subsequent Event [Member] | October 2017 Exercise Agreements [Member] | Series AAA and Series BBB Warrants [Member]
Class of Warrant or Right, Exercised During Period		4,665,000
Proceeds from Warrant Exercises		$ 20,000,000
Subsequent Event [Member] | October 2017 Exercise Agreements [Member] | Series AAA Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 2.07
Subsequent Event [Member] | October 2017 Exercise Agreements [Member] | Series BBB Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 4.75
Stock Issued During Period, Shares, Exercise of Warrants		205,000
Subsequent Event [Member] | October 2017 Exercise Agreements [Member] | Series DDD Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 6.20
Class of Warrant or Right, Issued During Period		1,166,250
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right		1
Class of Warrant or Right, Exercisable Period		180 days
Warrants Issued, Expiration Period		180 days
Subsequent Event [Member] | October 2017 Exercise Agreements [Member] | Series AA Warrant [Member]
Stock Issued During Period, Shares, Exercise of Warrants		108,455
Subsequent Event [Member] | October 2017 Undwriting Offering [Member]
Stock Issued During Period, Shares, New Issues	2,640,000
Common Stock, Par or Stated Value Per Share	$ 0.01
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	1,300,000
Shares Issued, Price Per Share	$ 2.325
Proceeds from Issuance of Common Stock and Warrants	$ 6,600,000
Subsequent Event [Member] | October 2017 Undwriting Offering [Member] | Investor Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 3
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right	1
Class of Warrant or Right, Exercisable Period	180 days
Warrants Issued, Expiration Period	5 years
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	1,320,000
Number of Warrants Sold with Each Share of Common Stock	0.5
Class of Warrant or Right, Offered Price of Warrants or Rights	$ 2.50
Subsequent Event [Member] | October 2017 Undwriting Offering [Member] | Investor Warrants [Member] | Underwriter [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	66,000