XML 202 R160.htm IDEA: XBRL DOCUMENT
v3.24.0.1

ASSET RETIREMENT OBLIGATIONS - Investment Securities in the Funds (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | $ 2,422 | $ 2,143
Equity securities |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | 1,288 | 1,095
Debt securities |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | 895 | 838
Other securities |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | 239 | 210
Alabama Power |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | 1,259 | 1,125
Alabama Power | Equity securities |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | 796 | 690
Alabama Power | Debt securities |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | 277 | 267
Alabama Power | Other securities |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | 186 | 168
Georgia Power |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | 1,163 | 1,018
Fair market value of securities on loan and pledged to creditors |  | 35
Fair value of collateral received |  | 36
Georgia Power | Equity securities |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | 492 | 405
Georgia Power | Debt securities |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | 618 | 571
Georgia Power | Other securities |  |
Marketable Securities [Line Items] |  |
Total investment securities in the Funds | $ 53 | $ 42

X
- Definition Decommissioning Fund Investments, Net Of Receivables + References No definition available. + Details
Name: | so_DecommissioningFundInvestmentsNetOfReceivables
Namespace Prefix: | so_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair market value of fund's securities on loan under fund's managers securities lending program. + References No definition available. + Details
Name: | so_FairMarketValueOfFundsSecuritiesOnLoanUnderFundsManagersSecuritiesLendingProgram
Namespace Prefix: | so_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair value of collateral received amount. + References No definition available. + Details
Name: | so_FairValueOfCollateralReceivedAmount
Namespace Prefix: | so_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition 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. + References No definition available. + Details
Name: | us-gaap_MarketableSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=so_OtherSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=so_AlabamaPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=so_GeorgiaPowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |