REGULATORY ASSETS, LIABILITIES, AND BALANCING ACCOUNTS (Long-Term Regulatory Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 6,604	$ 6,066
Retained generation asset costs	1,200
Pension benefits
Regulatory Assets [Line Items]
Total long-term regulatory assets	1,790	1,823
Environmental compliance costs
Regulatory Assets [Line Items]
Total long-term regulatory assets	1,053	1,062
Utility retained generation
Regulatory Assets [Line Items]
Total long-term regulatory assets	216	228
Price risk management
Regulatory Assets [Line Items]
Total long-term regulatory assets	138	124
Unamortized loss, net of gain, on reacquired debt
Regulatory Assets [Line Items]
Total long-term regulatory assets	59	63
Catastrophic event memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	684	656
Wildfire expense memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	443	423
Fire hazard prevention memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	260	259
Fire risk mitigation memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	96	95
Wild fire mitigation plan memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	840	558
Deferred income taxes
Regulatory Assets [Line Items]
Total long-term regulatory assets	468	252
Other
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 557	$ 523