Regulatory Matters - APC Reliability Reserve Accounting Matter (Details) - USD ($) $ in Millions |
Sep. 30, 2023 |
Aug. 18, 2023 |
Dec. 31, 2022 |
|---|---|---|---|
| Public Utilities, General Disclosures [Line Items] | |||
| Reliability reserve balance | $ 16 | $ 216 | |
| ALABAMA POWER CO | |||
| Public Utilities, General Disclosures [Line Items] | |||
| Reliability reserve balance | $ 71 | $ 97 | |
| Reliability Reserve | ALABAMA POWER CO | |||
| Public Utilities, General Disclosures [Line Items] | |||
| Reliability reserve balance | $ 166 |