INCOME TAXES - Reconciliation of Federal Statutory Income Tax Rate (Details)	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	21.00%	21.00%	21.00%
State income tax, net of federal deduction	2.60%	6.20%	5.50%
Employee stock plans' dividend deduction	(0.50%)	(0.50%)	(0.90%)
Non-deductible book depreciation	0.70%	0.60%	0.90%
Flowback of excess deferred income taxes	(9.20%)	(6.60%)	(11.70%)
AFUDC-Equity	(1.10%)	(1.10%)	(1.50%)
Federal PTCs	(1.20%)	0.00%	0.00%
ITC amortization	(1.30%)	(1.30%)	(2.20%)
Noncontrolling interests	0.60%	0.50%	0.80%
Leveraged lease impairments and dispositions			(1.40%)
Other	(0.20%)	0.00%	(0.10%)
Effective income tax (benefit) rate	11.40%	18.80%	10.40%
Alabama Power
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	21.00%	21.00%	21.00%
State income tax, net of federal deduction	5.20%	4.80%	4.60%
Employee stock plans' dividend deduction	0.00%	0.00%	0.00%
Non-deductible book depreciation	0.70%	0.50%	0.50%
Flowback of excess deferred income taxes	(19.80%)	(1.90%)	(2.60%)
AFUDC-Equity	(1.20%)	(0.80%)	(0.70%)
Federal PTCs	0.00%	0.00%	0.00%
ITC amortization	(0.10%)	(0.10%)	(0.10%)
Noncontrolling interests	0.00%	0.00%	0.00%
Leveraged lease impairments and dispositions			0.00%
Other	(0.20%)	0.30%	0.20%
Effective income tax (benefit) rate	5.60%	23.80%	22.90%
Georgia Power
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	21.00%	21.00%	21.00%
State income tax, net of federal deduction	1.50%	6.50%	(5.70%)
Employee stock plans' dividend deduction	0.00%	0.00%	0.00%
Non-deductible book depreciation	0.80%	0.60%	3.10%
Flowback of excess deferred income taxes	(2.60%)	(9.60%)	(49.90%)
AFUDC-Equity	(1.20%)	(1.50%)	(6.40%)
Federal PTCs	(1.40%)	0.00%	0.00%
ITC amortization	(0.10%)	(0.10%)	(0.40%)
Noncontrolling interests	0.00%	0.00%	0.00%
Leveraged lease impairments and dispositions			0.00%
Other	(0.30%)	0.00%	(1.90%)
Effective income tax (benefit) rate	17.70%	16.90%	(40.20%)
Mississippi Power
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	21.00%	21.00%	21.00%
State income tax, net of federal deduction	4.90%	4.40%	4.90%
Employee stock plans' dividend deduction	0.00%	0.00%	0.00%
Non-deductible book depreciation	0.40%	0.30%	0.40%
Flowback of excess deferred income taxes	(10.20%)	(7.80%)	(15.20%)
AFUDC-Equity	0.00%	0.00%	0.00%
Federal PTCs	0.00%	0.00%	0.00%
ITC amortization	0.00%	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%
Leveraged lease impairments and dispositions			0.00%
Other	0.10%	0.30%	0.60%
Effective income tax (benefit) rate	16.20%	18.20%	11.70%
Southern Power
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	21.00%	21.00%	21.00%
State income tax, net of federal deduction	(0.70%)	1.90%	(8.00%)
Employee stock plans' dividend deduction	0.00%	0.00%	0.00%
Non-deductible book depreciation	0.00%	0.00%	0.00%
Flowback of excess deferred income taxes	0.00%	0.00%	0.00%
AFUDC-Equity	0.00%	0.00%	0.00%
Federal PTCs	(7.40%)	(6.60%)	(4.60%)
ITC amortization	(19.00%)	(17.20%)	(29.70%)
Noncontrolling interests	11.10%	8.40%	13.40%
Leveraged lease impairments and dispositions			0.00%
Other	0.10%	(0.10%)	(0.40%)
Effective income tax (benefit) rate	5.10%	7.40%	(8.30%)
Southern Company Gas
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	21.00%	21.00%	21.00%
State income tax, net of federal deduction	7.80%	6.40%	15.10%
Employee stock plans' dividend deduction	0.00%	0.00%	0.00%
Non-deductible book depreciation	0.00%	0.00%	0.00%
Flowback of excess deferred income taxes	(2.60%)	(2.50%)	(2.80%)
AFUDC-Equity	0.00%	0.00%	0.00%
Federal PTCs	0.00%	0.00%	0.00%
ITC amortization	0.00%	(0.10%)	(0.10%)
Noncontrolling interests	0.00%	0.00%	0.00%
Leveraged lease impairments and dispositions			0.00%
Other	(0.60%)	(0.90%)	0.60%
Effective income tax (benefit) rate	25.60%	23.90%	33.80%

AFUDC equity.

No definition available.

Name:	so_AfudcEquity
Namespace Prefix:	so_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Effective Income Tax Rate Reconciliation Amortization Tax Credits Investment

+ References

No definition available.

+ Details

Name:	so_EffectiveIncomeTaxRateReconciliationAmortizationTaxCreditsInvestment
Namespace Prefix:	so_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Effective Income Tax Rate Reconciliation, Tax Credit, Production, Percent

+ References

No definition available.

+ Details

Name:	so_EffectiveIncomeTaxRateReconciliationTaxCreditProductionPercent
Namespace Prefix:	so_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-12

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateContinuingOperations
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-12

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.Fact.4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for dividend paid to employee stock ownership plan.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-12

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.Fact.4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationDeductionsEmployeeStockOwnershipPlanDividends
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to noncontrolling interest income (loss) exempt from income taxes.

+ References

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationMinorityInterestIncomeExpense
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

+ References

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseDepreciation
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

+ References

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseLeases
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

+ References

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to revisions of previously reported income tax expense.

+ References

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationPriorYearIncomeTaxes
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

+ References

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=so_AlabamaPowerMember
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_MississippiPowerMember
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: