CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Income Statement Equity Method Investment Carrying Amount (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2020 |
Jun. 30, 2019 |
Jun. 30, 2020 |
Jun. 30, 2019 |
|
| Schedule of Equity Method Investments [Line Items] | ||||
| Earnings from Equity Method Investments | $ 30 | $ 33 | $ 72 | $ 81 |
| SOUTHERN Co GAS | ||||
| Schedule of Equity Method Investments [Line Items] | ||||
| Earnings from Equity Method Investments | 30 | 31 | 72 | 80 |
| SOUTHERN Co GAS | SNG | ||||
| Schedule of Equity Method Investments [Line Items] | ||||
| Earnings from Equity Method Investments | 28 | 32 | 65 | 74 |
| SOUTHERN Co GAS | Atlantic Coast Pipeline | ||||
| Schedule of Equity Method Investments [Line Items] | ||||
| Earnings from Equity Method Investments | 0 | 3 | 3 | 6 |
| SOUTHERN Co GAS | PennEast Pipeline | ||||
| Schedule of Equity Method Investments [Line Items] | ||||
| Earnings from Equity Method Investments | 1 | 1 | 3 | 3 |
| SOUTHERN Co GAS | Other | ||||
| Schedule of Equity Method Investments [Line Items] | ||||
| Earnings from Equity Method Investments | $ 1 | $ (5) | $ 1 | $ (3) |