REVENUE FROM CONTRACTS WITH CUSTOMERS AND LEASE INCOME - Contract Balances (Details) - USD ($) $ in Millions |
Jun. 30, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Disaggregation of Revenue [Line Items] | ||
| Accounts Receivables | $ 2,283 | $ 2,413 |
| Contract Assets | 103 | 117 |
| Contract Liabilities | 57 | 52 |
| ALABAMA POWER CO | ||
| Disaggregation of Revenue [Line Items] | ||
| Accounts Receivables | 592 | 586 |
| Contract Assets | 0 | 0 |
| Contract Liabilities | 6 | 10 |
| GEORGIA POWER CO | ||
| Disaggregation of Revenue [Line Items] | ||
| Accounts Receivables | 796 | 688 |
| Contract Assets | 54 | 69 |
| Contract Liabilities | 23 | 13 |
| MISSISSIPPI POWER CO | ||
| Disaggregation of Revenue [Line Items] | ||
| Accounts Receivables | 84 | 79 |
| Contract Assets | 1 | 0 |
| Contract Liabilities | 0 | 0 |
| SOUTHERN POWER CO | ||
| Disaggregation of Revenue [Line Items] | ||
| Accounts Receivables | 115 | 97 |
| Contract Assets | 0 | 0 |
| Contract Liabilities | 1 | 1 |
| SOUTHERN Co GAS | ||
| Disaggregation of Revenue [Line Items] | ||
| Accounts Receivables | 523 | 749 |
| Contract Assets | 0 | 0 |
| Contract Liabilities | $ 2 | $ 1 |