Note 10 - Stockholders' Equity (Details) - Assumptions for Valuation of Waived Warrants Associated with Common Stock Offering	1 Months Ended	5 Months Ended	12 Months Ended
	Oct. 28, 2013	Jun. 03, 2013	Dec. 31, 2015
Note 10 - Stockholders' Equity (Details) - Assumptions for Valuation of Waived Warrants Associated with Common Stock Offering [Line Items]
Risk-free interest rate			0.78%
Expected volatility			102.23%
Expected life (in years)			5 years
Expected forfeiture rate	0.00%	0.00%	0.00%
Expected dividend yield	0.00%	0.00%	0.00%
Waived Warrants [Member] | Minimum [Member]
Note 10 - Stockholders' Equity (Details) - Assumptions for Valuation of Waived Warrants Associated with Common Stock Offering [Line Items]
Risk-free interest rate	0.59%	0.50%
Expected volatility	105.10%	102.90%
Expected life (in years)	2 years 255 days	3 years 36 days
Waived Warrants [Member] | Maximum [Member]
Note 10 - Stockholders' Equity (Details) - Assumptions for Valuation of Waived Warrants Associated with Common Stock Offering [Line Items]
Risk-free interest rate	1.31%	1.03%
Expected volatility	111.80%	110.90%
Expected life (in years)	4 years 109 days	4 years 255 days