Note 10 - Common Stock (Details) - Reserved for Future Issuances Shares of Common Stock	Dec. 31, 2014	Dec. 31, 2013
Note 10 - Common Stock (Details) - Reserved for Future Issuances Shares of Common Stock [Line Items]
Shares reserved for future issuance	1,947,849	5,810,472
Series A Preferred Stock [Member]
Note 10 - Common Stock (Details) - Reserved for Future Issuances Shares of Common Stock [Line Items]
Shares reserved for future issuance		1,426,482
Series A-1 Preferred Stock [Member]
Note 10 - Common Stock (Details) - Reserved for Future Issuances Shares of Common Stock [Line Items]
Shares reserved for future issuance		687,395
Series B Preferred Stock [Member]
Note 10 - Common Stock (Details) - Reserved for Future Issuances Shares of Common Stock [Line Items]
Shares reserved for future issuance		1,307,771
Series C Preferred Stock [Member]
Note 10 - Common Stock (Details) - Reserved for Future Issuances Shares of Common Stock [Line Items]
Shares reserved for future issuance		1,105,907
Performance Shares [Member]
Note 10 - Common Stock (Details) - Reserved for Future Issuances Shares of Common Stock [Line Items]
Shares reserved for future issuance	1,807,349	623,111
Employee Stock Purchase Plan [Member]
Note 10 - Common Stock (Details) - Reserved for Future Issuances Shares of Common Stock [Line Items]
Shares reserved for future issuance	140,500
Warrants To Purchase Common Stock [Member]
Note 10 - Common Stock (Details) - Reserved for Future Issuances Shares of Common Stock [Line Items]
Shares reserved for future issuance		659,806