XML 192 R148.htm IDEA: XBRL DOCUMENT
v3.22.0.1

PROPERTY, PLANT, AND EQUIPMENT - Composite Straight-Line Rates (Details) - Utility plant in service | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Alabama Power |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Composite rate | 2.70% | 2.60% | 3.10%
Georgia Power |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Composite rate | 3.30% | 3.00% | 2.60%
Mississippi Power |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Composite rate | 3.60% | 3.70% | 3.70%
Southern Company Gas |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Composite rate | 2.80% | 2.80% | 2.90%

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Composite depreciation rate for public utility plants in service. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=so_UtilityPlantInServiceMember
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_SouthernCompanyGasMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |