Note 9 - Preferred Stock (Details Textual) - USD ($) | Jul. 24, 2019 | Jul. 16, 2019 | Jun. 19, 2019 | Apr. 26, 2019 | Feb. 26, 2019 | Feb. 25, 2019 | Feb. 18, 2019 | Jul. 31, 2019 | Feb. 28, 2019 | Feb. 28, 2019 | Sep. 30, 2019 | Sep. 30, 2019 | Dec. 31, 2018 |
Preferred Stock, Shares Authorized | | | | | | | | | | | 10,000,000 | 10,000,000 | 10,000,000 |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | $ 0.01 | $ 0.01 | $ 0.01 |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | 3,054 | 3,054 | 3,450 |
Series I Warrants [Member] | | | | | | | | | | | | | |
Convertible Preferred Stock and Related Warrants Issued | | | | | 33,334 | | | | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights | | | | | $ 7.50 | | | | | | | | |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | | | | | 66,668 | | | | | | | | |
Series G Warrants [Member] | | | | | | | | | | | | | |
Warrants and Rights Outstanding, Term | | | | | 5 years | | | | | | | | |
Series G Convertible Preferred Stock and Related Warrants [Member] | | | | | | | | | | | | | |
Convertible Preferred Stock and Related Warrants, Authorized | | | | | | 1,000 | | | | | | | |
Proceeds from Issuance of Convertible Preferred Stock and Related Warrants, Maximum | | | $ 500,000 | $ 500,000 | $ 250,000 | $ 1,000,000 | | | | | | | |
Convertible Preferred Stock and Related Warrants Issued | | | 500 | 500 | 500 | | | | | | | | |
Conversion of Series C Preferred Stock Into Common Stock [Member] | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | | 587 | | 587 | |
Conversion of Stock, Shares Issued | | | | | | | | | | 78,280 | | 78,280 | |
Conversion of Series C Preferred Stock Into Series F Preferred Stock [Member] | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | 1,563 | | | 1,563 | |
Conversion of Series E Preferred Stock Into Series F Preferred Stock [Member] | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | 1,200 | | | 1,200 | |
Conversion of Series F Preferred Stock Into Common Stock [Member] | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | | | 46 | 507 | |
Conversion of Stock, Shares Issued | | | | | | | | | | | 88,400 | 381,700 | |
Conversion from Series F Preferred Stock to Series H Preferred Stock [Member] | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | 2,256 | | | | 2,256 | |
Conversion from Series F and Series G Preferred Stock to Series H Preferred Stock [Member] | | | | | | | | | | | | | |
Conversion of Stock, Shares Issued | | 3,256 | | | | | | | | | | 3,256 | |
Conversion of Series H Preferred Stock Into Common Stock [Member] | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | | | 1,002 | 1,002 | |
Conversion of Stock, Shares Issued | | | | | | | | | | | 94,687,441 | 94,687,441 | |
Conversion of Series I Preferred Stock [Member] | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | | | 0 | | |
Series B Convertible Preferred Stock [Member] | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | $ 1,000 | $ 1,000 | |
Conversion of Stock, Shares Converted | | | | | | | | | | | | 0 | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | 100 | 100 | 100 |
Convertible Preferred Stock, Conversion Price1 | | | | | | | | | | | $ 175 | $ 175 | |
Series E Convertible Preferred Stock [Member] | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | $ 1,000 | $ 1,000 | |
Conversion of Stock, Shares Converted | | | | | | | | | | | | 0 | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | | | 1,200 |
Series F Convertible Preferred Stock [Member] | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | | $ 1,000 | | | | $ 1,000 | $ 1,000 | |
Convertible Preferred Stock, Conversion Price1 | | | | | | | $ 7.50 | | | | | | |
Number of Series C and Series E Preferred Stock Exchanged for Series F Convertible Preferred Stock | | | | | | | 2,763 | | | | | | |
Convertible Preferred Stock, Conversion Price, Percentage of Volume Weighted Average Price of the Common Stock | | | | | | | 90.00% | | | | | | |
Series G Convertible Preferred Stock [Member] | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | $ 1,000 | | | | | $ 1,000 | $ 1,000 | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | 1,000 | | | | | |
Convertible Preferred Stock, Conversion Price1 | | | | | | $ 7.50 | | | | | | | |
Convertible Preferred Stock, Conversion Price, Percentage of Volume Weighted Average Price of the Common Stock | | | | | | 90.00% | | | | | | | |
Series H Convertible Preferred Stock [Member] | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | $ 1,000 | | | | | | | | | | | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | 2,254 | 2,254 | |
Convertible Preferred Stock, Conversion Price1 | | $ 7.50 | | | | | | | | | | | |
Series I Convertible Preferred Stock [Member] | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | $ 1,000 | | | | | | | | | | | | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | 700 | 700 | |
Convertible Preferred Stock, Conversion Price1 | $ 7.50 | | | | | | | | | | | | |
Stock Issued During Period, Shares, New Issues | 700 | | | | | | | | | | | | |
Proceeds from Issuance of Preferred Stock and Preference Stock | $ 700,000 | | | | | | | | | | | | |
Series C Convertible Preferred Stock [Member] | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | $ 1,000 | $ 1,000 | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | | | 2,150 |