CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Balance Sheet Equity Method Investment Carrying Amount (Details) - USD ($) $ in Millions |
Jun. 30, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Schedule of Equity Method Investments [Line Items] | ||
| Investment Balance | $ 1,363 | $ 1,303 |
| SOUTHERN Co GAS | ||
| Schedule of Equity Method Investments [Line Items] | ||
| Investment Balance | 1,308 | 1,251 |
| SOUTHERN Co GAS | SNG | ||
| Schedule of Equity Method Investments [Line Items] | ||
| Investment Balance | 1,189 | 1,137 |
| SOUTHERN Co GAS | PennEast Pipeline | ||
| Schedule of Equity Method Investments [Line Items] | ||
| Investment Balance | 87 | 82 |
| SOUTHERN Co GAS | Other | ||
| Schedule of Equity Method Investments [Line Items] | ||
| Investment Balance | $ 32 | $ 32 |