FAIR VALUE MEASUREMENTS (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets:
Short-term investments	$ 446	$ 1,323
Price risk management instruments, netting	46	(8)
Price risk management instruments, assets	215	158
TOTAL ASSETS	4,897	5,523
Liabilities:
Price risk management instruments, netting	(4)	(14)
TOTAL LIABILITIES	242	147
Amount primarily related to deferred taxes on appreciation of investment value	586	530
Nuclear decommissioning trusts
Assets:
Short-term investments	12	6
Global equity securities	2,222	2,086
Fixed-income securities	1,647	1,590
TOTAL ASSETS	3,904	3,703
Rabbi trusts
Assets:
Fixed-income securities	105	100
Life insurance contracts	78	73
TOTAL ASSETS	183	173
Long-term disability trust
Assets:
Short-term investments	5	10
TOTAL ASSETS	149	166
Price Risk Derivative, Electricity
Assets:
Price risk management instruments, netting	41	(11)
Price risk management instruments, assets	196	152
Liabilities:
Price risk management instruments, netting	(3)	(13)
Price risk management instruments, liabilities	240	146
Price Risk Derivative, Gas
Assets:
Price risk management instruments, netting	5	3
Price risk management instruments, assets	19	6
Liabilities:
Price risk management instruments, netting	(1)	(1)
Price risk management instruments, liabilities	2	1
Level 1
Assets:
Short-term investments	446	1,323
Price risk management instruments, gross subject to netting	0	0
TOTAL ASSETS	3,541	4,287
Liabilities:
TOTAL LIABILITIES	0	1
Level 1 | Nuclear decommissioning trusts
Assets:
Short-term investments	12	6
Global equity securities	2,222	2,086
Fixed-income securities	856	862
TOTAL ASSETS	3,090	2,954
Level 1 | Rabbi trusts
Assets:
Fixed-income securities	0	0
Life insurance contracts	0	0
TOTAL ASSETS	0	0
Level 1 | Long-term disability trust
Assets:
Short-term investments	5	10
TOTAL ASSETS	5	10
Level 1 | Price Risk Derivative, Electricity
Assets:
Price risk management instruments, gross subject to netting	0	0
Liabilities:
Price risk management instruments, gross subject to netting	0	1
Level 1 | Price Risk Derivative, Gas
Assets:
Price risk management instruments, gross subject to netting	0	0
Liabilities:
Price risk management instruments, gross subject to netting	0	0
Level 2
Assets:
Short-term investments	0	0
Price risk management instruments, gross subject to netting	27	5
TOTAL ASSETS	1,001	906
Liabilities:
TOTAL LIABILITIES	7	4
Level 2 | Nuclear decommissioning trusts
Assets:
Short-term investments	0	0
Global equity securities	0	0
Fixed-income securities	791	728
TOTAL ASSETS	791	728
Level 2 | Rabbi trusts
Assets:
Fixed-income securities	105	100
Life insurance contracts	78	73
TOTAL ASSETS	183	173
Level 2 | Long-term disability trust
Assets:
Short-term investments	0	0
TOTAL ASSETS	0	0
Level 2 | Price Risk Derivative, Electricity
Assets:
Price risk management instruments, gross subject to netting	13	2
Liabilities:
Price risk management instruments, gross subject to netting	4	2
Level 2 | Price Risk Derivative, Gas
Assets:
Price risk management instruments, gross subject to netting	14	3
Liabilities:
Price risk management instruments, gross subject to netting	3	2
Level 3
Assets:
Short-term investments	0	0
Price risk management instruments, gross subject to netting	142	161
TOTAL ASSETS	142	161
Liabilities:
TOTAL LIABILITIES	239	156
Level 3 | Nuclear decommissioning trusts
Assets:
Short-term investments	0	0
Global equity securities	0	0
Fixed-income securities	0	0
TOTAL ASSETS	0	0
Level 3 | Rabbi trusts
Assets:
Fixed-income securities	0	0
Life insurance contracts	0	0
TOTAL ASSETS	0	0
Level 3 | Long-term disability trust
Assets:
Short-term investments	0	0
TOTAL ASSETS	0	0
Level 3 | Price Risk Derivative, Electricity
Assets:
Price risk management instruments, gross subject to netting	142	161
Liabilities:
Price risk management instruments, gross subject to netting	239	156
Level 3 | Price Risk Derivative, Gas
Assets:
Price risk management instruments, gross subject to netting	0	0
Liabilities:
Price risk management instruments, gross subject to netting	0	0
Assets measured at NAV | Nuclear decommissioning trusts
Assets:
Assets measured at NAV	23	21
Assets measured at NAV | Long-term disability trust
Assets:
Assets measured at NAV	$ 144	$ 156