| Cover | Sep. 12, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 12, 2020 |
| Entity File Number | 000-12104 |
| Entity Registrant Name | IMMUNOMEDICS, INC. |
| Entity Central Index Key | 0000722830 |
| Entity Tax Identification Number | 61-1009366 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 300 The American Road |
| Entity Address, City or Town | Morris Plains |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 07950 |
| City Area Code | 973 |
| Local Phone Number | 605-8200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 par value |
| Trading Symbol | IMMU |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
