Note 10 - Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2014

Note 10 - Stockholders' Equity (Tables) [Line Items]

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year Ended December 31,
	2014				2013				2012
Risk-free interest rate	2.31	to	2.75	%	0.85	to	1.19	%	1.09	to	2.97	%
Expected volatility	94.3	-	100.7	%	83.4	-	97.9	%	80.8	-	82.3	%
Expected life (in years)		10			5.25	to	6.00		5.00	to	6.25
Expected forfeiture rate		10		%	5.0	to	7.5	%		7.5		%
Expected dividend yield		0.0		%		0.0		%		0.0		%

Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]

Shares of common stock associated with the Waived Warrants		Expiration Date of Waived Warrants	Strike Price		Per Share Fair Value on June 3, 2013		Per Share Fair Value on October 28, 2013
	1,323,496	2/26/2018	$	5.31	$	6.60	$	3.86
	31,243	7/25/2016	$	18.99	$	4.41	$	2.10
	12,628	7/6/2016	$	14.09	$	4.81	$	2.40
	31,448	11/25/2017	$	12.47	$	5.56	$	3.16

Prefered Stock [Member]

Note 10 - Stockholders' Equity (Tables) [Line Items]

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

Risk-free interest rate	0.78	%
Expected volatility	102.23	%
Expected life (in years)	5.0
Expected forfeiture rate	0.0	%
Expected dividend yield	0.0	%

Common Stock Offering [Member]

Note 10 - Stockholders' Equity (Tables) [Line Items]

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	June 3, 2013				October 28, 2013
Risk-free interest rate	0.50	-	1.03	%	0.59	-	1.31	%
Expected volatility	102.9	-	110.9	%	105.1	-	111.8	%
Expected life (in years)	3.1	-	4.7	%	2.7	-	4.3	%
Expected forfeiture rate		0.0		%		0.0		%
Expected dividend yield		0.00		%		0.00		%