Note 10 - Stockholders' Equity (Details Textual) - USD ($)									1 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended		24 Months Ended	47 Months Ended
	Dec. 20, 2016	Jun. 13, 2016	Oct. 02, 2015	May 27, 2015	Sep. 30, 2014	Jun. 20, 2014	Jan. 15, 2014	Feb. 01, 2013	Sep. 30, 2015	Feb. 25, 2013	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2016	Jun. 30, 2016	May 31, 2016	Dec. 31, 2014
Shelf Registration Statement Amount									$ 75,000,000
Common Stock, Shares Authorized													112,500,000	112,500,000	112,500,000	112,500,000	112,500,000	75,000,000
Preferred Stock, Shares Authorized													100,000	100,000	100,000	100,000	100,000
Aggregate of Common and Preferred Stock, Shares Authorized																	112,600,000
Class of Warrant or Right, Outstanding													20,831,883	5,894,675	20,831,883	20,831,883			5,069,815
Class of Warrant or Right, Exercise Price of Warrants or Rights													$ 1.88	$ 6.37	$ 1.88	$ 1.88			$ 8.18
Common Stock, Par or Stated Value Per Share													$ 0.01	$ 0.01	$ 0.01	$ 0.01
Proceeds from Warrant Exercises													$ 2,500		$ 0
Proceeds from Stock Options Exercised															$ 0
EGEN Inc [Member]
Stock Issued During Period, Shares, Acquisitions					2,712,188	2,712,188
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares					670,070							670,070
Common Stock [Member]
Stock Issued During Period, Shares, New Issues													126,518	14,000
June 2016 Common Stock Offering [Member]
Stock Issued During Period, Shares, New Issues		2,311,764
Share Price		$ 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		$ 1.40
Ownership Percentage, Restriction Threshold for Warrant Exercise		4.99%
Number of Days Notice Requirement to Increase or Decrease Beneficial Ownership Limitation		61 days
Common Stock Offering Period of Restriction		180 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
Class of Warrant or Right, Outstanding													1,850,000		1,850,000	1,850,000
June 2016 Common Stock Offering [Member] | Series B Warrant [Member] | Common Stock [Member]
Stock Issued During Period, Shares, Exercise of Warrants											250,000
June 2016 Common Stock Offering [Member] | Series A Warrant [Member]
Class of Warrant or Right, Outstanding		1,850,000
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right		0.5
Warrants Exercisable Period		180 days
Warrants Issued Expiration Period		5 years 182 days
June 2016 Common Stock Offering [Member] | Series C Warrant [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right		1
Warrants Exercisable Period		180 days
Warrants Issued Expiration Period		1 year
June 2016 Common Stock Offering [Member] | Series D Warrant [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right		0.5
Warrants Exercisable Period		180 days
Warrants Issued Expiration Period		5 years 182 days
December 2016 Common Stock Offering [Member]
Stock Issued During Period, Shares, New Issues	5,142,843
Share Price	$ 0.35
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	5,142,843
Maximum Beneficial Ownership of the Purchaser	9.99%
Proceeds from Issuance of Common Stock Gross	$ 1,800,000
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right	1
Warrants Exercisable Period	180 days
Warrants Issued Expiration Period	5 years 182 days
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 0.46
Number of Days Notice Requirement to Increase or Decrease Beneficial Ownership Limitation	61 days
May 2015 Common Stock Offering [Member]
Stock Issued During Period, Shares, New Issues				3,000,000
Share Price				$ 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				$ 2.60
Common Stock Offering Period of Restriction				150 days
January 2014 Common Stock Offering [Member]
Stock Issued During Period, Shares, New Issues							3,603,604
Share Price							$ 4.1625
Class of Warrant or Right, Number of Securities Called by Warrants or Rights							1,801,802
Class of Warrant or Right, Exercise Price of Warrants or Rights							$ 4.10
Common Stock Offering Period of Restriction							270 days
Common Stock, Par or Stated Value Per Share							$ 0.01
Stock Issued During Period, Value, New Issues							$ 15,000,000
Common Stock Shares per Unit							1
January 2014 Common Stock Offering [Member] | Series B Warrant [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right							0.25
Warrants Issued Expiration Period							1 year
January 2014 Common Stock Offering [Member] | Series A Warrant [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right							0.25
Warrants Issued Expiration Period							5 years
ATM Agreement [Member]
Stock Issued During Period, Shares, New Issues																1,479,535
Proceeds from Issuance of Common Stock Gross																$ 7,600,000
Aggregate Offering Price								$ 25,000,000					$ 17,400,000
Commission on Proceeds from ATM Shares Percent										3.00%
Legal Fees										$ 50,000
Aggregate Offering Price, Additions			$ 7,500,000										$ 7,500,000