Note 6 - Common Stock Reserved for Future Issuance (Details) - shares	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Performance Shares [Member]
Common Stock, Capital Shares Reserved for Future Issuance	3,007,453	2,419,901
The 2014 Employee Stock Purchase Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance	296,685	297,359	140,500
Common Stock, Capital Shares Reserved for Future Issuance	3,304,138	2,717,260