Note 3 - Basis of Presentation and Significant Accounting Policies - Valuation Assumptions (Details) - Fair Value, Inputs, Level 3 [Member] - $ / shares	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Series 2023 PIK Note Derivative Liability [Member]
Term (years) (Year)	6 years 29 days	6 years 211 days
Expected volatility	96.50%	86.20%
Risk-free interest rate	2.03%	2.18%
Market price and estimated fair value of stock (in dollars per share)	$ 0.04	$ 0.12
Exercise price (in dollars per share)	$ 1.28	$ 1.28
Series A PIK Note Derivative Liability [Member]
Term (years) (Year)	6 years 29 days	6 years 211 days
Expected volatility	96.50%	86.20%
Risk-free interest rate	2.03%	2.18%
Market price and estimated fair value of stock (in dollars per share)	$ 0.04	$ 0.12
Exercise price (in dollars per share)	$ 0.83	$ 0.83