| Document and Entity Information | Apr. 22, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | GORMAN RUPP CO |
| Amendment Flag | false |
| Entity Central Index Key | 0000042682 |
| Document Type | 8-K |
| Document Period End Date | Apr. 22, 2021 |
| Entity Incorporation State Country Code | OH |
| Entity File Number | 1-6747 |
| Entity Tax Identification Number | 34-0253990 |
| Entity Address, Address Line One | 600 South Airport Road |
| Entity Address, City or Town | Mansfield |
| Entity Address, State or Province | OH |
| Entity Address, Postal Zip Code | 44903 |
| City Area Code | (419) |
| Local Phone Number | 755-1011 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Shares, without par value |
| Trading Symbol | GRC |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
