XML 56 R28.htm IDEA: XBRL DOCUMENT
v3.24.3

Condensed Statements of Comprehensive Income - MPC (Parenthetical) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Changes in fair value, tax | $ (1) | $ 3 | $ (2) | $ (11)
Mississippi Power |  |  |  |
Changes in fair value, tax | $ 0 | $ 0 | $ 2 | $ 0

X
- Definition Amount, before reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-12 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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