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Introduction - Schedule of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024 | Sep. 30, 2024 | Dec. 31, 2023
--- | --- | --- | --- | ---
Restricted Cash and Cash Equivalent Item [Line Items] |  |  |  |
Cash and cash equivalents | $ 3,341 | $ 1,070 |  |
Restricted cash: |  |  |  |
Total cash, cash equivalents, and restricted cash | 3,342 | 1,101 | $ 1,055 | $ 921
Other current assets |  |  |  |
Restricted cash: |  |  |  |
Restricted cash | 1 | 31 |  |
GEORGIA POWER CO |  |  |  |
Restricted Cash and Cash Equivalent Item [Line Items] |  |  |  |
Cash and cash equivalents | 937 | 97 |  |
Restricted cash: |  |  |  |
Total cash, cash equivalents, and restricted cash | 937 | 118 | 64 | 75
GEORGIA POWER CO | Other current assets |  |  |  |
Restricted cash: |  |  |  |
Restricted cash | 0 | 21 |  |
SOUTHERN POWER CO |  |  |  |
Restricted Cash and Cash Equivalent Item [Line Items] |  |  |  |
Cash and cash equivalents | 1,047 | 159 |  |
Restricted cash: |  |  |  |
Total cash, cash equivalents, and restricted cash | 1,047 | 168 | 195 | 144
SOUTHERN POWER CO | Other current assets |  |  |  |
Restricted cash: |  |  |  |
Restricted cash | 0 | 9 |  |
SOUTHERN Co GAS |  |  |  |
Restricted Cash and Cash Equivalent Item [Line Items] |  |  |  |
Cash and cash equivalents | 346 | 43 |  |
Restricted cash: |  |  |  |
Total cash, cash equivalents, and restricted cash | 346 | 44 | $ 45 | $ 35
SOUTHERN Co GAS | Other current assets |  |  |  |
Restricted cash: |  |  |  |
Restricted cash | 0 | 1 |  |
SOUTHERN Co GAS | Collateral For Life Insurance And Long-Term Disability Insurance |  |  |  |
Restricted cash: |  |  |  |
Restricted cash |  | $ 1 |  |
Southern Holdings Company | Collateral For Life Insurance And Long-Term Disability Insurance |  |  |  |
Restricted cash: |  |  |  |
Restricted cash | $ 1 |  |  |

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- Definition Amount of cash and cash equivalent. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483467/210-10-45-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-4 + Details
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