Cover
| Cover | Jan. 08, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jan. 8, 2022 |
| Entity Registrant Name | Oglethorpe Power Corporation |
| Entity Incorporation, State or Country Code | GA |
| Entity File Number | 333-192954 |
| Entity Tax Identification Number | 58-1211925 |
| Entity Address, Address Line One | 2100 East Exchange Place |
| Entity Address, City or Town | Tucker |
| Entity Address, State or Province | GA |
| Entity Address, Postal Zip Code | 30084-5336 |
| City Area Code | 770 |
| Local Phone Number | 270-7600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000788816 |
| Amendment Flag | false |