Asset Retirement Obligations - Accumulated Provisions for the External Decommissioning Trust Funds (Details) - External decommissioning trust funds - USD ($) $ in Millions |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Georgia Power | ||
| Public Utilities, General Disclosures [Line Items] | ||
| Accumulated provisions for decommissioning | $ 873 | $ 929 |
| Plant Farley | Alabama Power | ||
| Public Utilities, General Disclosures [Line Items] | ||
| Accumulated provisions for decommissioning | 846 | 902 |
| Plant Hatch | Georgia Power | ||
| Public Utilities, General Disclosures [Line Items] | ||
| Accumulated provisions for decommissioning | 547 | 583 |
| Plant Vogtle Units 1 and 2 | Georgia Power | ||
| Public Utilities, General Disclosures [Line Items] | ||
| Accumulated provisions for decommissioning | $ 326 | $ 346 |