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INCOME TAXES - Changes in Unrecognized Tax Benefits (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Changes in unrecognized tax benefits [Roll Forward] |  |  |
Beginning balance | $ 80 | $ 47 | $ 44
Increase from prior periods | 88 | 33 | 3
Ending balance | 116 | 80 | 47
Estimated loss on plants under construction |  |  |
Changes in unrecognized tax benefits [Roll Forward] |  |  |
Statute of limitations expiration | (52) |  |
Georgia Power |  |  |
Changes in unrecognized tax benefits [Roll Forward] |  |  |
Beginning balance | 0 | 0 | 0
Increase from prior periods | 86 | 0 | 0
Ending balance | 77 | 0 | 0
Georgia Power | Estimated loss on plants under construction |  |  |
Changes in unrecognized tax benefits [Roll Forward] |  |  |
Statute of limitations expiration | (9) |  |
Southern Company Gas |  |  |
Changes in unrecognized tax benefits [Roll Forward] |  |  |
Beginning balance | 32 | 0 | 0
Increase from prior periods | 2 | 32 | 0
Ending balance | 34 | $ 32 | $ 0
Southern Company Gas | Estimated loss on plants under construction |  |  |
Changes in unrecognized tax benefits [Roll Forward] |  |  |
Statute of limitations expiration | $ 0 |  |

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- Definition Amount of unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-15A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 10B -Publisher FASB -URI https://asc.fasb.org//1943274/2147482525/740-10-45-10B + Details
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- Definition Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15A -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-15A + Details
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- Definition Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15A -Subparagraph (a)(4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-15A + Details
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