XML 144 R113.htm IDEA: XBRL DOCUMENT
v3.25.3

Derivatives - Schedule of Pre-Tax Effects of Hedging on AOCI (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | $ (18) | $ (2) | $ 48 | $ (7)
Cash Flow Hedging | Energy-related derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (12) | (7) | (6) | (11)
Cash Flow Hedging | Interest rate derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (1) | (8) | 6 | 16
Cash Flow Hedging | Foreign currency derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (6) | 15 | 60 | (4)
Fair Value Hedging | Foreign currency derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Amount excluded from effectiveness testing recognized in earnings | 1 | (2) | (12) | (8)
GEORGIA POWER CO | Cash Flow Hedging | Interest rate derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | 0 | 1 | 3 | 17
MISSISSIPPI POWER CO | Cash Flow Hedging | Interest rate derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | 0 | 0 | 0 | 7
SOUTHERN POWER CO |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (8) | 13 | 60 | (6)
SOUTHERN POWER CO | Cash Flow Hedging | Energy-related derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (2) | (2) | 0 | (2)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (6) | 15 | 60 | (4)
SOUTHERN Co GAS |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (11) | (10) | (3) | (14)
SOUTHERN Co GAS | Cash Flow Hedging | Energy-related derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | (10) | (4) | (6) | (9)
SOUTHERN Co GAS | Cash Flow Hedging | Interest rate derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Gain (Loss) Recognized in OCI on Derivatives | $ (1) | $ (6) | $ 3 | $ (5)

X
- 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 4C -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 182 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480401/815-10-55-182 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4D -Subparagraph (a)(5) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4D Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4D -Subparagraph (a)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4D Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4D -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4D Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4D -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4D Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4D -Subparagraph (a)(6) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4D Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4D -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4D Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4CCC -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4CCC Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4CCC -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4CCC Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4CCC -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4CCC Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4CC -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4CC Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 20: 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 Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4D -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4D Reference 22: 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

X
- Definition Net gain (loss) relating to components of the gain (loss) on the fair value hedging instrument excluded from the assessment of fair value hedge effectiveness. Recognized in earnings. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 21 -Subparagraph (i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147476148/220-40-50-21 + Details
Name: | us-gaap_GainLossFromComponentsExcludedFromAssessmentOfFairValueHedgeEffectivenessNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(19)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1 Reference 2: 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 3: 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

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

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

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

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

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

X
- Details
Name: | dei_LegalEntityAxis=so_GeorgiaPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=so_MississippiPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=so_SouthernPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=so_SouthernCompanyGasMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |