Note 9 - Net Loss Per Share Attributable to Common Stockholders - Common Stock Equivalents Excluded From Calculation of Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Convertible Preferred Stock [Member]
Anti-dilutive securities (in shares)		7,581		7,581
Common Stock Warrants [Member]
Anti-dilutive securities (in shares)		660		660
Employee Stock Option [Member]
Anti-dilutive securities (in shares)	1,800	1,134	1,800	1,134
Outstanding ESPP Shares [Member]
Anti-dilutive securities (in shares)	1		1
Anti-dilutive securities (in shares)	1,801	9,375	1,801	9,375