| Note 12 - Stock Warrants | 6 Months Ended | ||
|---|---|---|---|
| Jun. 30, 2020 | |||
| Notes to Financial Statements | |||
| Stock Warrants Disclosure [Text Block] | 
 In   May 2020,  411,000Series OO warrants to purchase the Company's common stock were exercised on a cashless basis in exchange for 300,595shares of Navidea common stock. As of   June 30, 2020, there are 991,874warrants outstanding to purchase Navidea's common stock. The warrants are exercisable at prices ranging from $0.20to $49.80per share with a weighted average exercise price of $18.37per share. The warrants have remaining outstanding terms ranging from oneto 15.1years. | 
| X | ||||||||||
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- Definition The entire disclosure for stock warrants. No definition available. 
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| X | ||||||||||
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- References No definition available. 
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