| Note 2 - Liquidity | 3 Months Ended | ||
|---|---|---|---|
| Mar. 31, 2021 | |||
| Notes to Financial Statements | |||
| Substantial Doubt about Going Concern [Text Block] | 
 As disclosed in the notes to the financial statements included in the Company's Annual Report on Form  10-K, the Company has been engaged in litigation with Platinum-Montaur Life Sciences LLC (“Platinum-Montaur”), an affiliate of Platinum Management (NY) LLC, Platinum Partners Value Arbitrage Fund L.P., Platinum Partners Capital Opportunity Fund, Platinum Partners Liquid Opportunity Master Fund L.P., Platinum Liquid Opportunity Management (NY) LLC, and Montsant Partners LLC (collectively, “Platinum”), in which Platinum-Montaur was seeking damages of approximately $1.9million plus interest.  See Note 11. In addition, the Company is engaged in ongoing litigation with our former President and Chief Executive Officer, Dr. Michael Goldberg. See Notes  7and 11. The Company has also been engaged in ongoing litigation with Capital Royalty Partners II L.P. (“CRG”) and pursuing recovery of approximately  $4.3million and other damages. See Note 11. On   August 30, 2020, the Company entered into a Stock Purchase Agreement (the “Common Stock Purchase Agreement”) with each of the investors named therein (the “Investors”), pursuant to which the Investors agreed to purchase from the Company, up to $25.0million in shares of the Company's common stock, par value $0.001per share (“Common Stock”). As of the date of filing of this Quarterly Report on Form 10-Q, we have received only $25,000of the $5.0million that is currently owed under the Common Stock Purchase Agreement. We are continuing to evaluate our rights and remedies under that agreement. See Note 12. On   August 31, 2020, the Company entered into a Stock Purchase Agreement and Letter of Investment Intent (the “Series D Preferred Stock Purchase Agreement”) with Keystone pursuant to which the Company agreed to issue to Keystone 150,000shares of newly-designated Series D Redeemable Convertible Preferred Stock (the “Series D Preferred Stock”) for an aggregate purchase price of $15.0million. Pursuant to the Series D Preferred Stock Purchase Agreement, Keystone will purchase Series D Preferred Stock in amounts to be determined by Keystone in oneor more closings. The Series D Preferred Stock will be convertible into a maximum of 5,147,000shares of Common Stock. As of the date of filing of this Quarterly Report on Form 10-Q, $5.5million has been received under the Series D Preferred Stock Purchase Agreement. See Notes 12and 17. On   March 2, 2021, the Company entered into a Stock Purchase Agreement and Letter of Investment Intent (the “Series E Preferred Stock Purchase Agreement”) with an existing accredited investor, John K. Scott, Jr. pursuant to which the Company issued to Mr. Scott in a private placement transaction 50,000shares of newly-designated Series E Redeemable Convertible Preferred Stock (the “Series E Preferred Stock”) for an aggregate purchase price of $5.0million. The Series E Preferred Stock is convertible into a maximum of 2,173,913shares of Common Stock. As of the date of filing of this Quarterly Report on Form 10-Q, noneof the Series E Preferred Stock has been converted. See Note 12. Navidea intends to use the net proceeds from these transactions to fund its research and development programs, including continued advancement of its  twoPhase 2band Phase 3clinical trials of Tc99mtilmanocept in patients with rheumatoid arthritis, and for general working capital purposes and other operating expenses. The Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) was enacted on   March 27, 2020. Among the provisions contained in the CARES Act was the creation of the Paycheck Protection Program (“PPP”) that provides for Small Business Administration (“SBA”) Section 7(a) loans for qualified small businesses. PPP loan proceeds are available to be used to pay for payroll costs, including salaries, commissions, and similar compensation, group health care benefits, and paid leaves; rent; utilities; and interest on certain other outstanding debt.  On  May 18, 2020, Fifth Third Bank (the “Lender”) funded a loan to the Company in the amount of $366,000under the SBA's PPP (the “PPP Loan”). In accordance with the loan forgiveness requirements of the CARES Act, the Company used the proceeds from the PPP Loan primarily for payroll costs, rent and utilities. On  February 23, 2021, the Lender notified the Company that the entire PPP Loan amount of $366,000was forgiven. See Note 9. During the ongoing COVID- 19global pandemic, the Company's primary focus is the safety of its employees, the employees of its clinical trial sites, and the patients enrolled in its clinical trials. The Company is working to mitigate any safety risk along with any long-term impact on its clinical development programs. Overall, we do notbelieve there has been an appreciable impact to the Company's clinical development and regulatory timelines resulting from COVID- 19.However, the COVID- 19outbreak has delayed enrollment in our NAV3- 32clinical study in the United Kingdom due to national COVID- 19-related shutdowns. The Company has experienced recurring net losses and has used significant cash to fund its operations. The Company has considerable discretion over the extent of development project expenditures and has the ability to curtail the related cash flows as needed. The Company also has funds remaining under outstanding grant awards, and continues working to establish new sources of funding, including collaborations, potential equity investments, and additional grant funding that can augment the balance sheet. Based on our committed equity investments, current working capital, and our projected cash burn, management believes that the Company will be able to continue as a going concern for a period of  oneyear from the filing of this Quarterly Report on Form 10-Q. |