| Cover Page Document | Nov. 26, 2019 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 26, 2019 |
| Entity File Number | 001-11229 |
| Entity Registrant Name | Mississippi Power Company |
| Entity Tax Identification Number | 64-0205820 |
| Entity Incorporation, State or Country Code | MS |
| Entity Address, Address Line One | 2992 West Beach Boulevard |
| Entity Address, City or Town | Gulfport |
| Entity Address, State or Province | MS |
| Entity Address, Postal Zip Code | 39501 |
| City Area Code | 228 |
| Local Phone Number | 864-1211 |
| 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 | 0000066904 |
| Amendment Flag | false |
