| Document and Entity Information | Jan. 27, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | GRAHAM CORP |
| Amendment Flag | false |
| Entity Central Index Key | 0000716314 |
| Document Type | 8-K |
| Document Period End Date | Jan. 27, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 1-08462 |
| Entity Tax Identification Number | 16-1194720 |
| Entity Address, Address Line One | 20 Florence Avenue |
| Entity Address, City or Town | Batavia |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 14020 |
| City Area Code | (585) |
| Local Phone Number | 343-2216 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.10 per share |
| Trading Symbol | GHM |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
