FINANCING - Bank Credit Arrangements (Details) $ in Millions	Dec. 31, 2023 USD ($)
Line of Credit Facility [Line Items]
2024	$ 280
2025	125
2026	800
2028	6,400
Total	7,605
Unused	7,566
Expires within One Year	280
Southern Company
Line of Credit Facility [Line Items]
2024	150
2025	0
2026	0
2028	1,850
Total	2,000
Unused	1,998
Expires within One Year	150
Alabama Power
Line of Credit Facility [Line Items]
2024	0
2025	0
2026	650
2028	700
Total	1,350
Unused	1,350
Expires within One Year	0
Georgia Power
Line of Credit Facility [Line Items]
2024	0
2025	0
2026	0
2028	1,750
Total	1,750
Unused	1,726
Expires within One Year	0
Mississippi Power
Line of Credit Facility [Line Items]
2024	0
2025	125
2026	150
2028	0
Total	275
Unused	275
Expires within One Year	0
Southern Power
Line of Credit Facility [Line Items]
2024	0
2025	0
2026	0
2028	600
Total	600
Unused	589
Expires within One Year	0
Southern Power \| Continuing Letter of Credit Facility A
Line of Credit Facility [Line Items]
2025	75
2026	100
Unused	8
Southern Power \| Continuing Letter of Credit Facility B
Line of Credit Facility [Line Items]
Unused	7
Southern Company Gas
Line of Credit Facility [Line Items]
2024	100
2025	0
2026	0
2028	1,500
Total	1,600
Unused	1,598
Expires within One Year	100
Other Subsidiaries
Line of Credit Facility [Line Items]
2024	30
2025	0
2026	0
2028	0
Total	30
Unused	30
Expires within One Year	30
Southern Company Gas Capital
Line of Credit Facility [Line Items]
Total	800
Nicor Gas
Line of Credit Facility [Line Items]
2024	100
Total	700
Southern Company and Southern Power
Line of Credit Facility [Line Items]
Line Of Credit Expire Year Five	$ 2,450

Bank credit arrangements no term loan due with in one year.

No definition available.

Name:	so_BankCreditArrangementsNoTermLoanDueWithInOneYear
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Expire Year Five

+ References

No definition available.

+ Details

Name:	so_LineOfCreditExpireYearFive
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Expire Year Four

+ References

No definition available.

+ Details

Name:	so_LineOfCreditExpireYearFour
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Expire Year One

+ References

No definition available.

+ Details

Name:	so_LineOfCreditExpireYearOne
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Expire Year Three

+ References

No definition available.

+ Details

Name:	so_LineOfCreditExpireYearThree
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Expire Year Two

+ References

No definition available.

+ Details

Name:	so_LineOfCreditExpireYearTwo
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=so_SouthernCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- 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:	us-gaap_CreditFacilityAxis=so_ContinuingLetterOfCreditFacilityAMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_CreditFacilityAxis=so_ContinuingLetterOfCreditFacilityBMember
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- Details

Name:	dei_LegalEntityAxis=so_SouthernCompanyGasMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	dei_LegalEntityAxis=so_OtherSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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

- Details

Name:	dei_LegalEntityAxis=so_NicorGasMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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