Note 8 - Stockholders' Deficit - Common Stock Reserved for Future Issuance (Details) - shares	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock options outstanding (in shares)	1,744,811
Shares available for grant under equity incentive plan (in shares)	19,549	732,149	1,060,400
Class of Warrant or Right, Outstanding	3,422,099
(in shares)	5,186,459