REGULATORY ASSETS, LIABILITIES, AND BALANCING ACCOUNTS (Long-Term Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	$ 8,539	$ 8,679
Cost of removal obligations
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	5,981	5,547
Deferred income tax
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	283	1,021
Recoveries in excess of AROs
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	356	624
Public purpose programs
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	674	590
Retirement Plan
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	421	418
Other
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	$ 824	$ 479