DERIVATIVES - Pre-Tax Effects of Derivatives Designated as Hedges on AOCI (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	$ (67)	$ 14	$ (154)
Energy-related derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	34	(8)	(13)
Interest rate derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	5	(26)	(57)
Foreign currency derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(103)	48	(84)
Foreign currency derivatives \| Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(3)	0	0
Georgia Power \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	0	(3)	(59)
Southern Power
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(91)	46	(88)
Southern Power \| Energy-related derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	12	(2)	(4)
Southern Power \| Foreign currency derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	(103)	48	(84)
Southern Company Gas
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	22	(29)	(7)
Southern Company Gas \| Energy-related derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	22	(6)	(9)
Southern Company Gas \| Interest rate derivatives \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) From Derivatives Recognized in OCI	$ 0	$ (23)	$ 2

Other Comprehensive Income (Loss), Derivative, Gain (Loss), after Reclassification, before Tax

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+ References

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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e637-108580

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Amount, before tax and after adjustments, of gain (loss) from increase (decrease) in value of excluded component of derivative designated and qualifying as hedge. Adjustments include, but are not limited to, reclassifications for sale and settlement, and amounts recognized under systematic and rational method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (dd)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669646-108580

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