DERIVATIVES - Pre-tax Effects of Derivatives Not Designated as Hedging (Details) - Derivatives not designated as hedging instruments - Energy-related derivatives - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2020 |
Jun. 30, 2019 |
Jun. 30, 2020 |
Jun. 30, 2019 |
|
| Derivative Instruments, Gain (Loss) [Line Items] | ||||
| Derivative instruments not designated as hedging instruments, gain (loss), net | $ 19 | $ 45 | $ 97 | $ 86 |
| Natural gas revenues | ||||
| Derivative Instruments, Gain (Loss) [Line Items] | ||||
| Derivative instruments not designated as hedging instruments, gain (loss), net | 14 | 50 | 84 | 83 |
| Cost of natural gas | ||||
| Derivative Instruments, Gain (Loss) [Line Items] | ||||
| Derivative instruments not designated as hedging instruments, gain (loss), net | $ 5 | $ (5) | $ 13 | $ 3 |