SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	$ 113	$ 44	$ 189	$ 44
Total regulatory balancing accounts receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Total regulatory balancing accounts, net	2,759		2,759		$ 2,001
Total regulatory balancing accounts receivable | Residential uncollectibles balancing accounts
Financing Receivable, Allowance for Credit Loss [Line Items]
Total regulatory balancing accounts, net	182		182		$ 0
COVID-19 pandemic protection memorandum account
Financing Receivable, Allowance for Credit Loss [Line Items]
Regulatory assets	26		26
Federal Energy Regulatory Commission (FERC)
Financing Receivable, Allowance for Credit Loss [Line Items]
Regulatory assets	$ 26		$ 26