Note 11 - Convertible Preferred Stock Warrant Liability - Warrants Outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Shares (in shares)	2,332,598
Estimated Fair Value		$ 275
Preferred Series D Warrant Issued January 2006 [Member]
Exercise price per share (in dollars per share)	$ 0.37
Value at grant date (in dollars per share)	$ 0.30
Shares (in shares)	325,861
Estimated Fair Value		2
Preferred Series D Warrant Issued July 2007 [Member]
Exercise price per share (in dollars per share)	$ 0.37
Value at grant date (in dollars per share)	$ 0.30
Shares (in shares)	203,691
Estimated Fair Value		20
Preferred Series D Warrant Issued August 2007 [Member]
Exercise price per share (in dollars per share)	$ 0.37
Value at grant date (in dollars per share)	$ 0.30
Shares (in shares)	203,691
Estimated Fair Value		20
Preferred Series D Warrants Issued September 2007 [Member]
Exercise price per share (in dollars per share)	$ 0.37
Value at grant date (in dollars per share)	$ 0.30
Shares (in shares)	203,691
Estimated Fair Value		20
Preferred Series F Warrant Issued April 2013 [Member]
Exercise price per share (in dollars per share)	$ 0.64
Value at grant date (in dollars per share)	$ 0.27
Shares (in shares)	888,176
Estimated Fair Value		94
Preferred Series F Warrant Issued April 2013 1 [Member]
Exercise price per share (in dollars per share)	$ 0.64
Value at grant date (in dollars per share)	$ 0.28
Shares (in shares)	482,699
Estimated Fair Value		115
Preferred Series F Warrant Issued April 2013 2 [Member]
Exercise price per share (in dollars per share)	$ 0.64
Value at grant date (in dollars per share)	$ 0.28
Shares (in shares)	11,620
Estimated Fair Value		3
Preferred Series F Warrant Issued May 2013 [Member]
Exercise price per share (in dollars per share)	$ 0.64
Value at grant date (in dollars per share)	$ 0.27
Shares (in shares)	13,169
Estimated Fair Value		$ 1