Regulatory Asset, Accrual

No definition available.

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Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Regulatory Asset, Weather-Related Damages

+ References

No definition available.

+ Details

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

- Definition

Amount of increase (decrease) in asset retirement obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 410
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481850/410-20-50-1

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount awarded from other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of public utility's approved rate increase (decrease) by regulatory agency.

+ References

No definition available.

+ Details

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

- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 340
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478742/980-340-50-1

+ Details

Name:	us-gaap_RegulatoryAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 405
-Name Accounting Standards Codification
-Section 25
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477571/980-405-25-1

+ Details

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

- Details

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- Details

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- Details

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Introduction - Storm Damage Reserves and Depreciation (Details) - USD ($) $ in Millions		1 Months Ended		9 Months Ended
	Apr. 01, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2025
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance at December 31, 2024				$ (705)
Balance at September 30, 2025			$ (705)	(856)
Accrued Storm Reserve
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Accrual				58
Storm Reserve
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Weather-related damages				(209)
ALABAMA POWER CO
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance at December 31, 2024				70
Balance at September 30, 2025				(4)
Balance at September 30, 2025			70
Amount awarded			7
Asset retirement obligation, period decrease		$ 257
ALABAMA POWER CO \| Accrued Storm Reserve
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Accrual				23
ALABAMA POWER CO \| Storm Reserve
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Weather-related damages				(97)
GEORGIA POWER CO
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance at December 31, 2024				(827)
Balance at September 30, 2025			(827)	(907)
GEORGIA POWER CO \| Accrued Storm Reserve
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Accrual				24
GEORGIA POWER CO \| Storm Reserve
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Weather-related damages				(104)
MISSISSIPPI POWER CO
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance at December 31, 2024				52
Balance at September 30, 2025			$ 52	55
Approved rate increase (decrease)	$ 8
Asset retirement obligation, period decrease		$ 13
MISSISSIPPI POWER CO \| Accrued Storm Reserve
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Accrual				11
MISSISSIPPI POWER CO \| Storm Reserve
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Weather-related damages				$ (8)