REGULATORY ASSETS, LIABILITIES, AND BALANCING ACCOUNTS (Long-Term Regulatory Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Regulatory Assets [Line Items]
Total long-term regulatory assets		$ 5,711	$ 4,964
Retained generation asset costs		1,200
Debtor reorganization items, write-off of debt issuance costs and debt discounts	$ 178
Pension benefits
Regulatory Assets [Line Items]
Total long-term regulatory assets		1,918	1,947
Environmental compliance costs
Regulatory Assets [Line Items]
Total long-term regulatory assets		1,067	1,013
Utility retained generation
Regulatory Assets [Line Items]
Total long-term regulatory assets		239	274
Price risk management
Regulatory Assets [Line Items]
Total long-term regulatory assets		140	90
Unamortized loss, net of gain, on reacquired debt
Regulatory Assets [Line Items]
Total long-term regulatory assets		66	76
Catastrophic event memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets		954	790
Wildfire expense memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets		143	94
Fire hazard prevention memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets		294	263
Fire risk mitigation memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets		109	0
Wild fire mitigation plan memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets		160	0
Other
Regulatory Assets [Line Items]
Total long-term regulatory assets		527	417
Deferred income taxes
Regulatory Assets [Line Items]
Total long-term regulatory assets		$ 94	$ 0