REGULATORY ASSETS, LIABILITIES, AND BALANCING ACCOUNTS (Long-Term Regulatory Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 7,986	$ 6,066
Retained generation asset costs	1,200
Pension benefits
Regulatory Assets [Line Items]
Total long-term regulatory assets	1,723	1,823
Environmental compliance costs
Regulatory Assets [Line Items]
Total long-term regulatory assets	1,089	1,062
Utility retained generation
Regulatory Assets [Line Items]
Total long-term regulatory assets	194	228
Price risk management
Regulatory Assets [Line Items]
Total long-term regulatory assets	209	124
Unamortized loss, net of gain, on reacquired debt
Regulatory Assets [Line Items]
Total long-term regulatory assets	53	63
Catastrophic event memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	771	656
Catastrophic event memorandum account | COVID-19
Regulatory Assets [Line Items]
Total long-term regulatory assets	41
Wildfire expense memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	419	423
Fire hazard prevention memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	259	259
Fire risk mitigation memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	99	95
Wild fire mitigation plan memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	1,080	558
Deferred income taxes
Regulatory Assets [Line Items]
Total long-term regulatory assets	729	252
Insurance premium costs
Regulatory Assets [Line Items]
Total long-term regulatory assets	588	0
COVID-19 pandemic protection memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	53	0
COVID-19 pandemic protection memorandum account, undercollection bad debt
Regulatory Assets [Line Items]
Total long-term regulatory assets	48
COVID-19 pandemic protection memorandum account, program and accounts receivable financing costs
Regulatory Assets [Line Items]
Total long-term regulatory assets	5
Other
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 720	$ 523