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STOCK COMPENSATION - Aggregate Intrinsic Value for Options Exercised (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Aggregate intrinsic value for options outstanding | $ 71 |  |
Aggregate intrinsic value for options exercisable | 71 |  |
Intrinsic value of options exercised | 34 | $ 38 | $ 167
Tax benefit of options exercised | 7 | 9 | 35
Alabama Power |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Intrinsic value of options exercised | 3 | 5 | 21
Tax benefit of options exercised | 1 | 1 | 4
Georgia Power |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Aggregate intrinsic value for options outstanding | 17 |  |
Aggregate intrinsic value for options exercisable | 17 |  |
Intrinsic value of options exercised | 14 | 9 | 30
Tax benefit of options exercised | 3 | $ 2 | $ 6
Southern Company Gas |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Aggregate intrinsic value for options outstanding | 8 |  |
Aggregate intrinsic value for options exercisable | $ 8 |  |

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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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