Note 11 - Stockholders' Equity (Details Textual)					1 Months Ended		3 Months Ended	38 Months Ended
	Jun. 13, 2016 USD ($) $ / shares shares	Oct. 02, 2015 USD ($)	May 27, 2015 USD ($) $ / shares shares	Feb. 02, 2013 USD ($)	Sep. 30, 2015 USD ($)	Feb. 25, 2013 USD ($)	Jun. 30, 2016 USD ($) $ / shares	Mar. 31, 2016 USD ($) shares	Dec. 31, 2015 $ / shares
June 2016 Common Stock Offering [Member] | Series A Warrant [Member]
Warrants Exercisable Period	180 days
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right	0.5
Warrants Issued Expiration Period	5 years 182 days
June 2016 Common Stock Offering [Member] | Series C Warrant [Member]
Warrants Exercisable Period	180 days
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right	1
Warrants Issued Expiration Period	1 year
June 2016 Common Stock Offering [Member] | Series D Warrant [Member]
Warrants Exercisable Period	180 days
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right	0.5
Warrants Issued Expiration Period	5 years 182 days
June 2016 Common Stock Offering [Member] | Series B Warrant [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	2,100,000
June 2016 Common Stock Offering [Member]
Stock Issued During Period, Shares, New Issues	2,311,764
Common Stock, Par or Stated Value Per Share | $ / shares	$ 0.01
Share Price | $ / shares	$ 1.36
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	8,823,528
Maximum Beneficial Ownership of the Purchaser	9.99%
Proceeds from Issuance of Common Stock Gross | $	$ 6,000,000
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares	$ 1.40
Ownership Percentage, Restriction Threshold for Warrant Exercise	4.99%
Number of Days Notice Requirement to Increase or Decrease Beneficial Ownership Limitation	61
May 2015 Common Stock Offering [Member]
Stock Issued During Period, Shares, New Issues			3,000,000
Share Price | $ / shares			$ 2.675
Class of Warrant or Right, Number of Securities Called by Warrants or Rights			1,950,000
Proceeds from Issuance of Common Stock Gross | $			$ 8,000,000
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right			0.65
Warrants Issued Expiration Period			5 years
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares			$ 2.60
Common Stock Offering PeriodOfRestriction			150 days
ATM Agreement [Member]
Stock Issued During Period, Shares, New Issues								1,479,535
Aggregate Offering Price | $				$ 25,000,000			$ 17,400,000
Proceeds from Issuance of Common Stock | $								$ 7,400,000
Commission on Proceeds from ATM Shares Percent						3.00%
Legal Fees | $						$ 50,000
Aggregate Offering Price, Additions | $		$ 7,500,000
Shelf Registration Statement Amount | $					$ 75,000,000
Common Stock, Par or Stated Value Per Share | $ / shares							$ 0.01		$ 0.01
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares							$ 2.97		$ 6.37
Aggregate Offering Price, Additions | $							$ 7,500,000