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ACQUISITIONS AND DISPOSITIONS - GAS Acquisitions and Dispositions Narrative (Details) $ in Millions |  | 1 Months Ended | 6 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Jul. 01, 2021 USD ($) | Dec. 31, 2020 USD ($) | Mar. 31, 2020 USD ($) payment | May 31, 2019 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Mar. 31, 2022 USD ($) | Apr. 22, 2021 USD ($)
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  |  |  |  | $ 176 | $ 66 | $ 2,588 |  |
Impairment charges |  |  |  |  |  |  | 2 | 0 | 168 |  |
Southern Company Gas |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  |  |  |  | 127 | 22 | 0 |  |
Impairment charges |  |  |  |  |  |  | 0 | 0 | 115 |  |
Southern Company Gas | Triton |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Realized loss on disposal |  |  |  | $ 6 |  |  |  |  |  |  |
Realized gain on disposal, net of tax |  |  |  | 7 |  |  |  |  |  |  |
Reversal of federal income tax valuation allowance |  |  |  | $ 13 |  |  |  |  | 13 |  |
Sequent | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Company Gas |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Consideration for sale | $ 159 |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions | 121 |  |  |  |  |  | 121 |  |  |  |
Gain (loss) on dispositions, after tax | $ 92 |  |  |  |  |  | 92 |  |  |  |
Deferred tax expense, increase from change in appointment rate |  |  |  |  | $ 85 | $ 85 | $ 85 |  |  |  |
Pivotal LNG | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Company Gas |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  |  |  |  |  |  | (24) |  |
Gain (loss) on dispositions, after tax |  |  |  |  |  |  |  |  | $ (17) |  |
Cash proceeds from sale of business |  |  | $ 178 |  |  |  |  |  |  |  |
Number of contingent milestone payments | payment |  |  | 2 |  |  |  |  |  |  |  |
Contingent milestone payment, amount |  |  |  |  |  |  |  |  |  |  | $ 5
Pivotal LNG | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Company Gas | Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Contingent milestone payment, amount |  |  |  |  |  |  |  |  |  | $ 5 |
Jefferson Island | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Company Gas | Natural Gas Storage Facility |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  | $ 22 |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions, after tax |  | 16 |  |  |  |  |  |  |  |  |
Cash proceeds from sale of business |  | $ 33 |  |  |  |  |  |  |  |  |
Impairment charges |  |  |  |  |  |  |  | 91 |  |  |
Impairment charges, after tax |  |  |  |  |  |  |  | $ 69 |  |  |

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