Regulatory Matters - Schedule of Cost Recovery Clauses (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
ALABAMA POWER CO \| Balance Sheet Location [Axis]: so:OtherRegulatoryAssetsCurrent
Loss Contingencies [Line Items]
Rate ECR	$ 7	$ 0
ALABAMA POWER CO \| Balance Sheet Location [Axis]: so:OtherRegulatoryAssetsDeferred
Loss Contingencies [Line Items]
Rate ECR	212	146
ALABAMA POWER CO \| Balance Sheet Location [Axis]: so:OtherRegulatoryLiabilitiesDeferred
Loss Contingencies [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	29	60
GEORGIA POWER CO \| Balance Sheet Location [Axis]: us-gaap:DeferredCosts
Loss Contingencies [Line Items]
Fuel cost recovery	151	212
GEORGIA POWER CO \| Balance Sheet Location [Axis]: so:OtherRegulatoryAssetsCurrent \| Property Damage Reserve Asset
Loss Contingencies [Line Items]
Regulatory asset balance related to storm damage	187	31
GEORGIA POWER CO \| Balance Sheet Location [Axis]: so:OtherRegulatoryAssetsDeferred \| Property Damage Reserve Asset
Loss Contingencies [Line Items]
Regulatory asset balance related to storm damage	784	880
GEORGIA POWER CO \| Balance Sheet Location [Axis]: so:UnderRecoveredFuelClauseRevenuesReceivablesCurrent
Loss Contingencies [Line Items]
Fuel cost recovery	161	310
MISSISSIPPI POWER CO \| Wholesale MB
Loss Contingencies [Line Items]
Fuel cost recovery	0	0
MISSISSIPPI POWER CO \| Balance Sheet Location [Axis]: us-gaap:AccountsReceivableGrossCurrent \| Wholesale MRA
Loss Contingencies [Line Items]
Fuel cost recovery	10	6
MISSISSIPPI POWER CO \| Balance Sheet Location [Axis]: us-gaap:DeferredCosts
Loss Contingencies [Line Items]
Fuel cost recovery	0	40
MISSISSIPPI POWER CO \| Balance Sheet Location [Axis]: so:OtherRegulatoryLiabilitiesDeferred \| Retail electric revenues
Loss Contingencies [Line Items]
Property damage reserve	56	57
MISSISSIPPI POWER CO \| Balance Sheet Location [Axis]: so:UnderRecoveredFuelClauseRevenuesReceivablesCurrent
Loss Contingencies [Line Items]
Fuel cost recovery	55	0
SOUTHERN Co GAS \| Balance Sheet Location [Axis]: so:NaturalGasCostOverRecoveryShortTerm
Loss Contingencies [Line Items]
Natural gas cost under recovery	$ 191	$ 158

Over (Under) recovered fuel balance.

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- Definition

Regulatory Clause, Property Damage Reserve

+ References

No definition available.

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- Definition

Retail Energy Cost Recovery

+ References

No definition available.

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- Definition

Carrying amount as of the balance sheet date of capitalized gas costs of a regulated entity that are expected to be recoverable through rate adjustments within one year or the normal operating cycle, if longer.

+ References

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- Definition

Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims.

+ References

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- 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.

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- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

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