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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

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- 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 -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 + Details
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- Definition 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 + Details
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