| Document and Entity Information | Oct. 01, 2019 |
| Cover [Abstract] | |
| Entity Registrant Name | NEOGEN CORP |
| Entity Address, State or Province | MI |
| Amendment Flag | false |
| Entity Central Index Key | 0000711377 |
| Document Type | 8-K |
| Document Period End Date | Oct. 1, 2019 |
| Entity File Number | 0-17988 |
| Entity Tax Identification Number | 38-2367843 |
| Entity Address, Address Line One | 620 Lesher Place |
| Entity Address, City or Town | Lansing |
| Entity Incorporation, State or Country Code | MI |
| Entity Address, Postal Zip Code | 48912 |
| City Area Code | 517 |
| Local Phone Number | 372-9200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
