REGULATORY ASSETS, LIABILITIES, AND BALANCING ACCOUNTS (Long-Term Regulatory Liabilities) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	$ 11,661	$ 10,424
Proceeds received from sale of transmission tower wireless licenses, refunded to customers	455
Federal Energy Regulatory Commission (FERC)
Regulatory Liabilities [Line Items]
Proceeds received from sale of transmission tower wireless licenses, refunded to customers	314
California Public Utilities Commission (CPUC)
Regulatory Liabilities [Line Items]
Proceeds received from sale of transmission tower wireless licenses, refunded to customers	141
Cost of removal obligations
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	7,216	6,905
Recoveries in excess of AROs
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	306	458
Public purpose programs
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	974	948
Employee benefit plans
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	1,022	995
Tower Licenses
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	455	0
SFGO Sale
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	359	0
Other
Regulatory Liabilities [Line Items]
Total long-term regulatory liabilities	$ 1,329	$ 1,118