| Significant Accounting Policies [Text Block] | 
      |  | Summary of Significant Accounting Policies |          |  |  | 
Basis of Presentation:  The information presented as of   March 31, 2021  and for the  three -month periods ended   March 31, 2021  and  2020  is unaudited, but includes all adjustments (which consist only of normal recurring adjustments) that the management of Navidea Biopharmaceuticals, Inc. (“Navidea”, the “Company,” or “we”) believes to be necessary for the fair presentation of results for the periods presented. Certain prior period amounts also have been reclassified to conform to the current year's presentation. In addition, certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) have been condensed or omitted pursuant to the rules and regulations of the U.S. Securities and Exchange Commission. The balances as of   March 31, 2021  and the results for the interim periods are  not  necessarily indicative of results to be expected for the year. The consolidated financial statements should be read in conjunction with Navidea's audited consolidated financial statements for the year ended   December 31, 2020,  which were included as part of our Annual Report on Form  10 -K.   Our consolidated financial statements include the accounts of Navidea and our wholly owned subsidiaries, Navidea Biopharmaceuticals Europe Limited (“Navidea Europe”) and Navidea Biopharmaceuticals Limited (“Navidea UK”), as well as those of our majority-owned subsidiary, Macrophage Therapeutics, Inc. (“MT”). All significant inter-company accounts were eliminated in consolidation.   During the ongoing COVID- 19  global 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  not  believe there has been an appreciable impact to the Company's clinical development and regulatory timelines resulting from COVID- 19.  However, the COVID- 19  outbreak has delayed enrollment in our  NAV3 - 32  clinical study in the United Kingdom due to national COVID- 19 -related shutdowns. The extent to which COVID- 19  impacts our operations and financial results will depend on numerous evolving factors that we are  not  able to accurately predict, including: the duration and scope of the pandemic, government actions taken in response to the pandemic, and the impact on our ability to continue to conduct our clinical trials. |          |  |  | 
Financial Instruments and Fair Value:  The following methods and assumptions were used to estimate the fair value of each class of financial instruments: |          |  |  | 
Cash and cash equivalents, stock subscriptions and other receivables, and accounts payable:  The carrying amounts approximate fair value because of the short maturity of these instruments. |          |  |  | 
Notes payable:  The carrying value of our debts as of   March 31, 2021  and   December 31, 2020  primarily consisted of the face amount of the notes plus accrued interest. As of   March 31, 2021  and   December 31, 2020,  the fair value of our notes payable was approximately  $191,000  and  $745,000,  both amounts equal to the carrying value of the notes payable. See Note  9. |          |  |  | 
Revenue Recognition:  We currently generate revenue from grants to support various product development initiatives. We generally recognize grant revenue when expenses reimbursable under the grants have been paid and payments under the grants become contractually due.   We also earn revenues related to our licensing and distribution agreements. The consideration we are eligible to receive under our licensing and distribution agreements typically includes upfront payments, reimbursement for research and development costs, milestone payments, and royalties. Each licensing and distribution agreement is unique and requires separate assessment in accordance with current accounting standards. See Note  3. |          |  |  | 
Leases:  All of our leases are operating leases and are included in right-of-use lease assets, current lease liabilities and noncurrent lease liabilities on our consolidated balance sheets. These assets and liabilities are recognized at the commencement date based on the present value of remaining lease payments over the lease term using the Company's incremental borrowing rates or implicit rates, when readily determinable. The discount rates used for each lease were based principally on the Platinum debt, which was secured and outstanding for most of  2018.  We used a “build-up” method where the approach was to estimate the risk/credit spread priced into the debt rate and then adjust that for the remaining term of each lease. Additionally, some market research was completed on the Company's peer group. Short-term operating leases which have an initial term of  12  months or less are  not  recorded on the consolidated balance sheets. Lease expense for operating leases is recognized on a straight-line basis over the lease term. Lease expense is included in selling, general and administrative expenses on our consolidated statements of operations. See Note  10. |          |  |  | 
Series D and Series E Convertible Preferred Stock:  The Company evaluated the provisions of the Series D and Series E Preferred Stock under Accounting Standards Codification (“ASC”)  480, Distinguishing Liabilities from Equity , ASC  815, Derivatives and Hedging , ASC  470, Debt , and Accounting Series Release (“ASR”)  268, Presentation in Financial Statements of  “ Redeemable Preferred Stocks .” Based on this evaluation, the Company determined that neither the Series D nor Series E Preferred Stock is a mandatorily redeemable financial instrument and any obligation to issue a variable number of shares of Common Stock is  not  unconditional. Accordingly, the Series D and Series E Preferred Stock should be classified as equity. Neither the embedded conversion option nor the embedded call option meet the criteria to be separated from the Series D or Series E Preferred stock and thus these features should  not  be bifurcated and accounted for as derivatives. Additionally, the Series D Preferred Stock contains a beneficial conversion feature (“BCF”). Prior to the adoption of Accounting Standards Update (“ASU”)  No. 2020 - 06, Accounting for Convertible Instruments and Contracts in an Entity ' s Own Equity , effective   January 1, 2021,  the BCF resulted in an increase to additional paid-in capital and a discount on the Series D Preferred Stock. The discount on the Series D Preferred Stock was considered to be fully amortized at the date of issuance because the Series D Preferred Stock is immediately convertible, resulting in a deemed dividend at the date of issuance for the amount of the BCF. Finally, the Company determined that the Series D and Series E Preferred Stock does  not  contain conversion features that could result in the Company being required to redeem a portion of the shares converted, thus the Series D and Series E Preferred Stock should  not  be classified in mezzanine equity. See Note  12. |          |  |  | 
Recently Adopted Accounting Standards:  In   December 2019,  the Financial Accounting Standards Board (“FASB”) issued ASU  No. 2019 - 12, Income Taxes (Topic  740 ): Simplifying the Accounting for Income Taxes. ASU  2019 - 12  is intended to improve consistent application and simplify the accounting for income taxes. ASU  2019 - 12  removes certain exceptions to the general principles in Topic  740  and clarifies and amends existing guidance. ASU  2019 - 12  is effective for annual and interim reporting periods beginning after   December 12, 2020,  with early adoption permitted. The adoption of ASU  2019 - 12  did  not  have a material impact on our consolidated financial statements.   In   August 2020,  the FASB issued ASU  No. 2020 - 06, Accounting for Convertible Instruments and Contracts in an Entity ' s Own Equity . ASU  2020 - 06  was issued to reduce the complexity associated with accounting for certain financial instruments with characteristics of liabilities and equity. ASU  2020 - 06  reduces the number of accounting models for convertible debt instruments and convertible preferred stock and improves the disclosures for convertible instruments and related earnings-per-share (“EPS”) guidance. ASU  2020 - 06  also amends the guidance for the derivatives scope exception for contracts in an entity's own equity and improves and amends the related EPS guidance. ASU  2020 - 06  is effective for public business entities except smaller reporting companies for annual and interim reporting periods beginning after   December 15, 2021,  and for annual and interim reporting periods beginning after   December 15, 2023  for all other entities. Early adoption is permitted, but the guidance must be adopted as of the beginning of a fiscal year. We adopted ASU  2020 - 06  effective   January 1, 2021  using the modified retrospective method. The adoption of ASU  2020 - 06  did  not  result in a cumulative effect adjustment to retained earnings. |          |  |  | 
Recently Issued Accounting Standards:  In   May 2021,  the FASB Issued ASU  No. 2021 - 04, Issuer ' s Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options . ASU  2021 - 04  was issued to clarify and reduce diversity in an issuer's accounting for modifications or exchange of freestanding equity-classified written call options (for example, warrants) that remain equity-classified after modification or exchange.  ASU2 021 - 04  requires that an entity treat a modification or exchange of a freestanding equity-classified written call option that remains equity-classified after modification or exchange be treated as an exchange of the original instrument for a new instrument.  ASU2021 - 04  also clarifies how an entity should measure and recognize the effect of a modification or exchange of a freestanding equity-classified written call option that remains equity-classified after modification or exchange. ASU  2021 - 04  is effective for all entities for fiscal years beginning after   December 15, 2021,  including interim periods within those fiscal years, and should be implemented prospectively to modifications or exchanges occurring on or after the effective date of the amendments. Early adoption is permitted, including in an interim period. We do  not  expect the adoption of ASU  2021 - 04  to have a material impact on our consolidated financial statements. |  |