REGULATORY ASSETS, LIABILITIES, AND BALANCING ACCOUNTS (Long-Term Regulatory Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	$ 9,251	$ 9,270
Cost of removal obligations
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	6,593	6,456
Recoveries in excess of AROs
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	66	393
Public purpose programs
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	903	817
Employee benefit plans
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	760	750
Other
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	$ 929	$ 854