REGULATORY ASSETS, LIABILITIES, AND BALANCING ACCOUNTS (Long-Term Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	$ 10,424	$ 9,270
Cost of removal obligations
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	6,905	6,456
Recoveries in excess of AROs
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	458	393
Public purpose programs
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	948	817
Retirement Plan
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	995	750
Other
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	$ 1,118	$ 854