DERIVATIVES - Interest Rate Derivatives (Details) - Interest rate derivatives $ in Millions	12 Months Ended
Dec. 31, 2021 USD ($)
Derivative [Line Items]
Notional Amount	$ 1,900
Fair Value Gain (Loss) December 31, 2021	(10)
Southern Company \| Fair Value Hedges of Existing Debt \| March 2028
Derivative [Line Items]
Notional Amount	$ 400
Interest Rate Received	1.75%
Weighted Average Interest Rate Paid	0.68%
Fair Value Gain (Loss) December 31, 2021	$ (5)
Southern Company \| Fair Value Hedges of Existing Debt \| April 2030
Derivative [Line Items]
Notional Amount	$ 1,000
Interest Rate Received	3.70%
Weighted Average Interest Rate Paid	2.36%
Fair Value Gain (Loss) December 31, 2021	$ (6)
SOUTHERN Co GAS \| Fair Value Hedges of Existing Debt
Derivative [Line Items]
Notional Amount	$ 500
Interest Rate Received	1.75%
Weighted Average Interest Rate Paid	0.38%
Fair Value Gain (Loss) December 31, 2021	$ 1

Fair value gain (Loss).

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- Definition

Notional amount of interest rate derivatives, interest rate paid.

+ References

No definition available.

+ Details

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- Definition

Notional amount of interest rate derivatives, interest rate received.

+ References

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- 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

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

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