FAIR VALUE MEASUREMENTS (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Assets:
Short-term investments	$ 1,717	$ 1,323
Price risk management instruments, netting	5	(8)
Price risk management instruments, assets	173	158
TOTAL ASSETS	5,640	5,523
Liabilities:
Price risk management instruments, netting	(7)	(14)
TOTAL LIABILITIES	162	147
Amount primarily related to deferred taxes on appreciation of investment value	498	530
Nuclear decommissioning trusts
Assets:
Short-term investments	82	6
Global equity securities	1,792	2,086
Fixed-income securities	1,518	1,590
TOTAL ASSETS	3,409	3,703
Rabbi trusts
Assets:
Fixed-income securities	102	100
Life insurance contracts	76	73
TOTAL ASSETS	178	173
Long-term disability trust
Assets:
Short-term investments	6	10
TOTAL ASSETS	163	166
Price Risk Derivative, Electricity
Assets:
Price risk management instruments, netting	5	(11)
Price risk management instruments, assets	171	152
Liabilities:
Price risk management instruments, netting	(7)	(13)
Price risk management instruments, liabilities	162	146
Price Risk Derivative, Gas
Assets:
Price risk management instruments, netting	0	3
Price risk management instruments, assets	2	6
Liabilities:
Price risk management instruments, netting	0	(1)
Price risk management instruments, liabilities	0	1
Level 1
Assets:
Short-term investments	1,717	1,323
Price risk management instruments, gross subject to netting	0	0
TOTAL ASSETS	4,381	4,287
Liabilities:
TOTAL LIABILITIES	0	1
Level 1 | Nuclear decommissioning trusts
Assets:
Short-term investments	82	6
Global equity securities	1,792	2,086
Fixed-income securities	784	862
TOTAL ASSETS	2,658	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	6	10
TOTAL ASSETS	6	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	9	5
TOTAL ASSETS	921	906
Liabilities:
TOTAL LIABILITIES	5	4
Level 2 | Nuclear decommissioning trusts
Assets:
Short-term investments	0	0
Global equity securities	0	0
Fixed-income securities	734	728
TOTAL ASSETS	734	728
Level 2 | Rabbi trusts
Assets:
Fixed-income securities	102	100
Life insurance contracts	76	73
TOTAL ASSETS	178	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	7	2
Liabilities:
Price risk management instruments, gross subject to netting	5	2
Level 2 | Price Risk Derivative, Gas
Assets:
Price risk management instruments, gross subject to netting	2	3
Liabilities:
Price risk management instruments, gross subject to netting	0	2
Level 3
Assets:
Short-term investments	0	0
Price risk management instruments, gross subject to netting	159	161
TOTAL ASSETS	159	161
Liabilities:
TOTAL LIABILITIES	164	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	159	161
Liabilities:
Price risk management instruments, gross subject to netting	164	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	17	21
Assets measured at NAV | Long-term disability trust
Assets:
Assets measured at NAV	$ 157	$ 156