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Minimum Natural Disaster Reserve Balance, Triggering Establishment Charge

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Natural Disaster Reserve, Expected Annual Recovery Until Reserve is Restored

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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The proportionate share of interest (percent) in a jointly owned utility plant.

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Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Regulatory Matters - APC (Details)	3 Months Ended	9 Months Ended
Regulatory Matters - APC (Details)	Dec. 31, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 23, 2021 MW	Apr. 15, 2021	Dec. 31, 2020 USD ($)
Public Utilities, General Disclosures [Line Items]
Construction work in progress			$ 9,611,000,000			$ 8,697,000,000
ALABAMA POWER CO
Public Utilities, General Disclosures [Line Items]
Construction work in progress			1,129,000,000			866,000,000
Minimum natural disaster reserve balance, triggering establishment charge			50,000,000
Natural disaster reserve authorized limit			75,000,000
Natural disaster reserve balance			36,000,000
Natural disaster reserve, expected annual recovery until reserve is restored			16,000,000
ALABAMA POWER CO \| Calhoun Power Company, LLC
Public Utilities, General Disclosures [Line Items]
Approximate nameplate capacity (in MWs) \| MW				743
ALABAMA POWER CO \| Scenario, Forecast \| Subsequent Event
Public Utilities, General Disclosures [Line Items]
Natural disaster reserve, expected recovery amount	$ 4,000,000
ALABAMA POWER CO \| Scenario, Forecast \| Calhoun Power Company, LLC
Public Utilities, General Disclosures [Line Items]
Purchase price		$ 180,000,000
ALABAMA POWER CO \| Plant Barry Unit 8
Public Utilities, General Disclosures [Line Items]
Construction work in progress			222,000,000
MISSISSIPPI POWER CO
Public Utilities, General Disclosures [Line Items]
Construction work in progress			$ 117,000,000			$ 146,000,000
MISSISSIPPI POWER CO \| Plant Greene County Units 1 and 2 \| ALABAMA POWER CO
Public Utilities, General Disclosures [Line Items]
Proportionate ownership share					40.00%