FAIR VALUE MEASUREMENTS (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Assets:
Short-term investments	$ 718	$ 1,323
Price risk management instruments, netting	22	(8)
Price risk management instruments, assets	189	158
TOTAL ASSETS	4,981	5,523
Liabilities:
Price risk management instruments, netting	(7)	(14)
TOTAL LIABILITIES	1,720	147
Amount primarily related to deferred taxes on appreciation of investment value	540	530
Nuclear decommissioning trusts
Assets:
Short-term investments	34	6
Global equity securities	2,135	2,086
Fixed-income securities	1,547	1,590
TOTAL ASSETS	3,736	3,703
Rabbi trusts
Assets:
Fixed-income securities	105	100
Life insurance contracts	77	73
TOTAL ASSETS	182	173
Long-term disability trust
Assets:
Short-term investments	6	10
TOTAL ASSETS	156	166
Equity Backstop Commitments and Forward Stock Purchase Agreements
Liabilities:
Derivative liability	1,500
Price Risk Derivative, Electricity
Assets:
Price risk management instruments, netting	21	(11)
Price risk management instruments, assets	183	152
Liabilities:
Price risk management instruments, netting	(6)	(13)
Price risk management instruments, liabilities	217	146
Price Risk Derivative, Gas
Assets:
Price risk management instruments, netting	1	3
Price risk management instruments, assets	6	6
Liabilities:
Price risk management instruments, netting	(1)	(1)
Price risk management instruments, liabilities	3	1
Level 1
Assets:
Short-term investments	718	1,323
Price risk management instruments, gross subject to netting	0	0
TOTAL ASSETS	3,687	4,287
Liabilities:
TOTAL LIABILITIES	0	1
Level 1 | Nuclear decommissioning trusts
Assets:
Short-term investments	34	6
Global equity securities	2,135	2,086
Fixed-income securities	794	862
TOTAL ASSETS	2,963	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 | Equity Backstop Commitments and Forward Stock Purchase Agreements
Liabilities:
Derivative liability	0
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	19	5
TOTAL ASSETS	954	906
Liabilities:
TOTAL LIABILITIES	1,513	4
Level 2 | Nuclear decommissioning trusts
Assets:
Short-term investments	0	0
Global equity securities	0	0
Fixed-income securities	753	728
TOTAL ASSETS	753	728
Level 2 | Rabbi trusts
Assets:
Fixed-income securities	105	100
Life insurance contracts	77	73
TOTAL ASSETS	182	173
Level 2 | Long-term disability trust
Assets:
Short-term investments	0	0
TOTAL ASSETS	0	0
Level 2 | Equity Backstop Commitments and Forward Stock Purchase Agreements
Liabilities:
Derivative liability	1,500
Level 2 | Price Risk Derivative, Electricity
Assets:
Price risk management instruments, gross subject to netting	14	2
Liabilities:
Price risk management instruments, gross subject to netting	9	2
Level 2 | Price Risk Derivative, Gas
Assets:
Price risk management instruments, gross subject to netting	5	3
Liabilities:
Price risk management instruments, gross subject to netting	4	2
Level 3
Assets:
Short-term investments	0	0
Price risk management instruments, gross subject to netting	148	161
TOTAL ASSETS	148	161
Liabilities:
TOTAL LIABILITIES	214	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 | Equity Backstop Commitments and Forward Stock Purchase Agreements
Liabilities:
Derivative liability	0
Level 3 | Price Risk Derivative, Electricity
Assets:
Price risk management instruments, gross subject to netting	148	161
Liabilities:
Price risk management instruments, gross subject to netting	214	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	20	21
Assets measured at NAV | Long-term disability trust
Assets:
Assets measured at NAV	$ 150	$ 156