XML 138 R107.htm IDEA: XBRL DOCUMENT
v3.25.3

Derivatives - Schedule of Energy-Related Derivatives (Details) - Energy-related, Natural Gas MMBTU in Millions | Sep. 30, 2025 MMBTU
--- | ---
Energy-related derivative contracts |
Net Purchased mmBtu | 443.0
ALABAMA POWER CO |
Energy-related derivative contracts |
Net Purchased mmBtu | 132.0
GEORGIA POWER CO |
Energy-related derivative contracts |
Net Purchased mmBtu | 123.0
MISSISSIPPI POWER CO |
Energy-related derivative contracts |
Net Purchased mmBtu | 101.0
SOUTHERN POWER CO |
Energy-related derivative contracts |
Net Purchased mmBtu | 9.0
SOUTHERN Co GAS |
Energy-related derivative contracts |
Net Purchased mmBtu | 78.0
SOUTHERN Co GAS | Energy-related derivatives not designated as hedging instruments | Long |
Energy-related derivative contracts |
Derivative nonmonetary notional amount net long short position volume | 96.0
SOUTHERN Co GAS | Energy-related derivatives not designated as hedging instruments | Short |
Energy-related derivative contracts |
Derivative nonmonetary notional amount net long short position volume | 18.0

X
- Definition Derivative Nonmonetary Notional Amount Net Long Short Position Volume + References No definition available. + Details
Name: | so_DerivativeNonmonetaryNotionalAmountNetLongShortPositionVolume
Namespace Prefix: | so_
Data Type: | dtr-types:energyItemType
Balance Type: | na
Period Type: | instant

X
- Definition Energy-related derivative contracts for the registrants. + References No definition available. + Details
Name: | so_EnergyRelatedDerivativeContractsForRegistrantsAbstract
Namespace Prefix: | so_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Net Quantity Purchase Of Derivatives Not Designated As Hedges + References No definition available. + Details
Name: | so_NetQuantityPurchaseOfDerivativesNotDesignatedAsHedges
Namespace Prefix: | so_
Data Type: | dtr-types:energyItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_PublicUtilitiesInventoryNaturalGasMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=so_AlabamaPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=so_GeorgiaPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=so_MississippiPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=so_SouthernPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=so_SouthernCompanyGasMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PositionAxis=us-gaap_LongMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PositionAxis=us-gaap_ShortMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |