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ACQUISITIONS AND DISPOSITIONS - Southern Company Narrative (Details) |  |  | 1 Months Ended | 3 Months Ended | 12 Months Ended |  |
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Dec. 13, 2021 USD ($) project | Oct. 29, 2021 USD ($) | Dec. 31, 2019 USD ($) leveraged_lease | Jan. 31, 2019 USD ($) | Dec. 31, 2021 USD ($) | Jun. 30, 2021 USD ($) | Dec. 31, 2020 USD ($) | Jun. 30, 2020 USD ($) | Dec. 31, 2019 USD ($) | Sep. 30, 2019 USD ($) | Jun. 30, 2019 USD ($) | Dec. 31, 2021 USD ($) project | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 30, 2019 USD ($) | Jul. 31, 2019 USD ($)
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  |  |  |  |  |  |  |  |  | $ 176,000,000 | $ 66,000,000 | $ 2,588,000,000 |  |
Impairment charges |  |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |
Number of domestic projects subject to leveraged lease sold | project |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |
Lease, initial impairment loss |  |  |  |  |  |  | $ 34,000,000 |  |  |  |  |  |  |  |  |
Lease, initial impairment loss, after tax |  |  |  |  |  |  | 17,000,000 |  |  |  |  |  |  |  |  |
Lease, impairment loss |  |  |  |  |  |  |  | $ 154,000,000 | $ 17,000,000 |  |  | $ 7,000,000 | 206,000,000 | 0 |  |
Lease, impairment loss, after tax |  |  |  |  |  |  |  | $ 74,000,000 | 13,000,000 |  |  |  |  |  |  |
Proceeds from sale of assets subject to leveraged lease | $ 673,000,000 | $ 45,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on sale of assets subject to leveraged lease |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leveraged leases, income tax benefits |  |  |  |  | $ 16,000,000 |  |  |  |  |  |  |  |  |  |  |
Number of international projects subject to leveraged lease terminated | project | 2 |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |
Gain (loss) on termination of leveraged leases |  |  |  |  |  |  |  |  |  |  |  | $ 93,000,000 |  |  |  |
Gain (loss) on termination of leveraged leases, after tax |  |  |  |  |  |  |  |  |  |  |  | $ 99,000,000 |  |  |  |
All Other |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lease, impairment loss |  |  |  |  |  | $ 7,000,000 | 18,000,000 |  |  |  |  |  | 206,000,000 |  |  |
Lease, impairment loss, after tax |  |  |  |  |  | $ 6,000,000 | $ 14,000,000 |  |  |  |  |  | $ 105,000,000 |  |  |
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Gulf Power |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash proceeds from sale of business |  |  |  | $ 5,800,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Indebtedness assumed |  |  |  | 1,300,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  | 2,600,000,000 |  |  |  |  |  |  |  |  |  | 2,600,000,000 |  |
Gain (loss) on dispositions, after tax |  |  |  | $ 1,400,000,000 |  |  |  |  |  |  |  |  |  | 1,400,000,000 |  |
Disposal Group, Disposed of by Sale, Not Discontinued Operations | PowerSecure Utility Infrastructure Services Unit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consideration for sale |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 65,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | PowerSecure International, Inc. Lighting Business |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash proceeds from sale of business |  |  | $ 4,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Indebtedness assumed |  |  | 5,000,000 |  |  |  |  |  | 5,000,000 |  |  |  |  | 5,000,000 |  |
Gain (loss) on dispositions |  |  |  |  |  |  |  |  |  |  |  |  |  | (58,000,000) |  |
Gain (loss) on dispositions, after tax |  |  |  |  |  |  |  |  |  |  |  |  |  | (52,000,000) |  |
Consideration for sale |  |  | $ 9,000,000 |  |  |  |  |  | $ 9,000,000 |  |  |  |  | $ 9,000,000 |  |
Disposal Group, Held-for-sale, Not Discontinued Operations | PowerSecure Utility Infrastructure Services Unit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Impairment charges |  |  |  |  |  |  |  |  |  |  | $ 32,000,000 |  |  |  |  |
Disposal Group, Held-for-sale, Not Discontinued Operations | PowerSecure International, Inc. Lighting Business |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Goodwill and intangible asset impairment |  |  |  |  |  |  |  |  |  | $ 18,000,000 |  |  |  |  |  |
Disposal Group, Held-for-sale, Not Discontinued Operations | Leveraged Lease Investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consideration for sale |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 20,000,000 |
Number of domestic projects subject to leveraged lease sold | leveraged_lease |  |  | 1 |  |  |  |  |  |  |  |  |  |  |  |  |

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