| Document and Entity Information | Jul. 01, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | II-VI INC |
| Amendment Flag | false |
| Entity Central Index Key | 0000820318 |
| Current Fiscal Year End Date | --06-30 |
| Document Type | 8-K |
| Document Period End Date | Jul. 1, 2020 |
| Entity File Number | 0-16195 |
| Entity Incorporation State Country Code | PA |
| Entity Tax Identification Number | 25-1214948 |
| Entity Address, Address Line One | 375 Saxonburg Boulevard |
| Entity Address, City or Town | Saxonburg |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 16056 |
| City Area Code | (724) |
| Local Phone Number | 352-4455 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, no par value |
| Trading Symbol | IIVI |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
