SEGMENT AND RELATED INFORMATION - Electric Utilities' Revenues (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Revenue from External Customer [Line Items] | |||
| Total operating revenues | $ 21,419 | $ 23,495 | $ 23,031 |
| Retail electric revenues | |||
| Revenue from External Customer [Line Items] | |||
| Total operating revenues | 14,084 | 15,222 | 15,330 |
| Other electric revenues | |||
| Revenue from External Customer [Line Items] | |||
| Total operating revenues | 636 | 664 | 681 |
| Electric Utilities | |||
| Revenue from External Customer [Line Items] | |||
| Total operating revenues | 17,095 | 18,571 | 18,540 |
| Electric Utilities | Retail electric revenues | |||
| Revenue from External Customer [Line Items] | |||
| Total operating revenues | 14,084 | 15,222 | 15,330 |
| Electric Utilities | Wholesale | |||
| Revenue from External Customer [Line Items] | |||
| Total operating revenues | 2,152 | 2,516 | 2,426 |
| Electric Utilities | Other electric revenues | |||
| Revenue from External Customer [Line Items] | |||
| Total operating revenues | $ 859 | $ 833 | $ 784 |