Introduction - Intangibles, Amortization (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended |
|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2019 |
|
| Finite-Lived Intangible Assets [Line Items] | ||
| Amortization of intangible assets | $ 15 | $ 32 |
| SOUTHERN POWER CO | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Amortization of intangible assets | 4 | 10 |
| SOUTHERN Co GAS | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Amortization of intangible assets | 8 | 16 |
| Gas Marketing Services | SOUTHERN Co GAS | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Amortization of intangible assets | 6 | 12 |
| Wholesale Gas Services | SOUTHERN Co GAS | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Amortization of intangible assets | $ 2 | $ 4 |