| Document and Entity Information | Jun. 01, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | GRAHAM CORP |
| Amendment Flag | true |
| Entity Central Index Key | 0000716314 |
| Document Type | 8-K/A |
| Document Period End Date | Jun. 1, 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 |
| Amendment Description | On June 3, 2021, Graham Corporation (the “Company”) filed a Current Report on Form 8-K (the “Original Report”) to report the acquisition of Barber-Nichols LLC, a Colorado limited liability company (“BN”). The Company is hereby filing this Current Report on Form 8-K/A (the “Amendment”) to amend Item 9.01 of the Original Report to present the required financial statements and pro forma financial information. Except for the filing of such financial statements and pro forma financial information this Amendment does not modify or update the Original Report. |
