Note 8 - Common Stock - Common Stock Reserved for Future Issuance (Details) - shares	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2014
Reserved for future issuance (in shares)	664,961	684,871
The 2014 Employee Stock Purchase Plan [Member]
Reserved for future issuance (in shares)	2,953	2,953	3,513
Performance Shares [Member]
Reserved for future issuance (in shares)	185,729	129,099
Conversion of Series A Preferred Stock to Common Stock [Member]
Reserved for future issuance (in shares)	476,279	552,819