| Note 15 - Supplemental Disclosure for Statements of Cash Flows | 9 Months Ended | ||
|---|---|---|---|
| Sep. 30, 2020 | |||
| Notes to Financial Statements | |||
| Cash Flow, Supplemental Disclosures [Text Block] | 
 During the  nine-month periods ended  September 30, 2020 and 2019,we paid interest aggregating $5,000and $6,000,respectively. During the nine-month period ended  September 30, 2020, we issued 94,159shares of our common stock valued at $172,000to our employees as partial payment in lieu of cash for their 2019bonuses. During the nine-month periods ended  September 30, 2020 and 2019,we issued 32,651and 8,128shares of our common stock as matching contributions to our 401(k) Plan which were valued at $40,000and $20,000,respectively. During the nine-month period ended  September 30, 2020,  411,000Series OO warrants to purchase the Company's common stock were exercised on a cashless basis in exchange for issuance of 300,595shares of Navidea common stock. During the nine-month period ended  September 30, 2020, the Company recorded a deemed dividend of approximately $467,000related to the BCF on 420,000shares of Series C Preferred Stock, and 420,000shares of Series C Preferred Stock were converted into 1,425,076shares of Common Stock. Also during the nine-month period ended  September 30, 2020, the Company recorded a deemed dividend of approximately $17,000related to the BCF on 1,500shares of Series D Preferred Stock, and 1,500shares of Series D Preferred Stock were converted into 56,497shares of Common Stock. |