REGULATORY ASSETS, LIABILITIES, AND BALANCING ACCOUNTS (Long-Term Regulatory Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 4,964	$ 3,793
Utility retained generation asset costs	1,200
Pension benefits
Regulatory Assets [Line Items]
Total long-term regulatory assets	1,947	1,954
Environmental compliance costs
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 1,013	837
Recovery Period	32 years
Utility retained generation
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 274	319
Recovery Period	8 years
Price risk management
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 90	65
Recovery Period	10 years
Unamortized loss, net of gain, on reacquired debt
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 76	79
Recovery Period	25 years
Catastrophic event memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 790	274
Wildfire expense memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	94	0
Fire hazard prevention memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	263	1
Other
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 417	$ 264