Debt Instrument, Face Amount, Remarketed

No definition available.

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
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

No definition available.

+ Details

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

- Definition

The cash inflow from the additional capital contribution to the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3255-108585

+ Details

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

- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=so_Series2019ARemarketableJuniorSubordinatedNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_JuniorSubordinatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=so_Series2019BRemarketableJuniorSubordinatedNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=so_A2019SeriesAEquityUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

FINANCING - Equity Units (Details) - USD ($) $ in Thousands		12 Months Ended
FINANCING - Equity Units (Details) - USD ($) $ in Thousands	Aug. 01, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	May 31, 2022
Debt Instrument [Line Items]
Proceeds from issuance of common stock		$ 1,808,000	$ 73,000	$ 74,000
Series 2019A Remarketable Junior Subordinated Notes \| Junior subordinated notes
Debt Instrument [Line Items]
Remarketed principal amount					$ 862,500
Quarterly interest rate					4.475%
Series 2019B Remarketable Junior Subordinated Notes \| Junior subordinated notes
Debt Instrument [Line Items]
Remarketed principal amount					$ 862,500
Quarterly interest rate					5.113%
2019 Series A Equity Units \| Junior subordinated notes
Debt Instrument [Line Items]
Common stock issued to settle purchase contracts (in shares)	25,200,000
Proceeds from issuance of common stock	$ 1,725,000