DERIVATIVES - Pre-Tax Effects of Derivatives Designated as Hedges on AOCI (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	$ (58)	$ (80)	$ (67)
Energy-related derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(81)	3	34
Interest rate derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(12)	46	5
Foreign currency derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	14	(105)	(103)
Foreign currency derivatives \| Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	21	(24)	(3)
Georgia Power \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(2)	31	0
Southern Power
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(4)	(120)	(91)
Southern Power \| Energy-related derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(18)	(15)	12
Southern Power \| Foreign currency derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	14	(105)	(103)
Southern Company Gas \| Energy-related derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	$ (63)	$ 18	$ 22

Other Comprehensive Income (Loss), Derivative, Gain (Loss), after Reclassification, before Tax

No definition available.

Name:	so_OtherComprehensiveIncomeLossDerivativeGainLossAfterReclassificationBeforeTax
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4E
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4E

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before tax and after reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-11

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 10A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-10A

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, before tax and after adjustments, of gain (loss) from increase (decrease) in value of excluded component of derivative designated and qualifying as hedge. Adjustments include, but are not limited to, reclassifications for sale and settlement, and amounts recognized under systematic and rational method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 10A
-Subparagraph (dd)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-10A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4C
-Subparagraph (bb)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4C

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseAfterAdjustmentsBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_EnergyRelatedDerivativeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_FairValueHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=so_GeorgiaPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=so_SouthernPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=so_SouthernCompanyGasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: