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

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477548/944-605-55-15

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
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-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477548/944-605-55-12

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
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 S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
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-Name Accounting Standards Codification
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-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
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-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

+ 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
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

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-Topic 210
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

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-Topic 210
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
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-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ 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:
Period Type:

- 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:	us-gaap_CreditFacilityAxis=so_UncommitedLetterOfCreditFacilityMember
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:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=so_ContinuingLetterOfCreditFacilityBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	dei_LegalEntityAxis=so_NicorGasMember
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Balance Type:
Period Type:

Financing - Schedule of Credit Arrangements (Details) - USD ($) $ in Millions	Sep. 30, 2025	Mar. 31, 2025	Feb. 28, 2025
Line of Credit Facility [Line Items]
2026	$ 45
2027	625
2029	650
2030	7,600
Total	8,920
Unused	8,909
Expires within One Year	30
Southern Company parent
Line of Credit Facility [Line Items]
2026	0
2027	500
2029	0
2030	2,500
Total	3,000
Unused	2,999
Expires within One Year	0
2028			$ 150
ALABAMA POWER CO
Line of Credit Facility [Line Items]
2026	15
2027	0
2029	650
2030	700
Total	1,365
Unused	1,365
Expires within One Year	0
GEORGIA POWER CO
Line of Credit Facility [Line Items]
2026	0
2027	0
2029	0
2030	2,050		1,750
Total	2,050
Unused	2,042
Expires within One Year	0
GEORGIA POWER CO \| Uncommited Letter Of Credit Facility
Line of Credit Facility [Line Items]
Letters of credit outstanding	26
MISSISSIPPI POWER CO
Line of Credit Facility [Line Items]
2026	0
2027	125
2029	0
2030	150
Total	275
Unused	275
Expires within One Year	0
SOUTHERN POWER CO
Line of Credit Facility [Line Items]
2026	0
2027	0
2029	0
2030	600
Total	600
Unused	600
Expires within One Year	0
SOUTHERN POWER CO \| Continuing Letter of Credit Facility A
Line of Credit Facility [Line Items]
Total	75
Unused	17
SOUTHERN POWER CO \| Continuing Letter of Credit Facility B
Line of Credit Facility [Line Items]
Total	100
Unused	4
SOUTHERN POWER CO \| Uncommited Letter Of Credit Facility
Line of Credit Facility [Line Items]
Letters of credit outstanding	23
SOUTHERN Co GAS
Line of Credit Facility [Line Items]
2026	0
2027	0
2029	0		1,500
2030	1,600
Total	1,600
Unused	1,598
Expires within One Year	0
SEGCO
Line of Credit Facility [Line Items]
2026	30
2027	0
2029	0
2030	0
Total	30
Unused	30
Expires within One Year	30
Southern Company, Southern Power, And Mississippi Power
Line of Credit Facility [Line Items]
2030	3,250
Total		$ 3,250	$ 2,450
Alabama Property Company
Line of Credit Facility [Line Items]
2026	15
Unused	15
Southern Company Gas Capital
Line of Credit Facility [Line Items]
2030	800	800
Nicor Gas
Line of Credit Facility [Line Items]
2030	$ 800	$ 800