FAIR VALUE MEASUREMENTS (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Assets:
Short-term investments	$ 3,402	$ 1,593
Price risk management instruments, netting	44	88
Price risk management instruments, assets	252	297
TOTAL ASSETS	7,477	5,350
Liabilities:
Price risk management instruments, netting	(7)	(10)
TOTAL LIABILITIES	85	109
Amount primarily related to deferred taxes on appreciation of investment value	491	408
Nuclear decommissioning trusts
Assets:
Short-term investments	16	29
Global equity securities	1,959	1,793
Fixed-income securities	1,513	1,300
TOTAL ASSETS	3,507	3,138
Rabbi trusts
Assets:
Fixed-income securities	98	93
Life insurance contracts	71	67
TOTAL ASSETS	169	160
Long-term disability trust
Assets:
Short-term investments	5	7
TOTAL ASSETS	147	162
Price Risk Derivative, Electricity
Assets:
Price risk management instruments, netting	20	51
Price risk management instruments, assets	225	259
Liabilities:
Price risk management instruments, netting	(4)	(10)
Price risk management instruments, liabilities	83	107
Price Risk Derivative, Gas
Assets:
Price risk management instruments, netting	24	37
Price risk management instruments, assets	27	38
Liabilities:
Price risk management instruments, netting	(3)	0
Price risk management instruments, liabilities	2	2
Level 1
Assets:
Short-term investments	3,402	1,593
Price risk management instruments, gross subject to netting	0	0
TOTAL ASSETS	6,197	4,083
Liabilities:
TOTAL LIABILITIES	2	4
Level 1 | Nuclear decommissioning trusts
Assets:
Short-term investments	16	29
Global equity securities	1,959	1,793
Fixed-income securities	815	661
TOTAL ASSETS	2,790	2,483
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	7
TOTAL ASSETS	5	7
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	4
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	2	0
Level 2
Assets:
Short-term investments	0	0
Price risk management instruments, gross subject to netting	16	6
TOTAL ASSETS	883	805
Liabilities:
TOTAL LIABILITIES	7	7
Level 2 | Nuclear decommissioning trusts
Assets:
Short-term investments	0	0
Global equity securities	0	0
Fixed-income securities	698	639
TOTAL ASSETS	698	639
Level 2 | Rabbi trusts
Assets:
Fixed-income securities	98	93
Life insurance contracts	71	67
TOTAL ASSETS	169	160
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	5
Liabilities:
Price risk management instruments, gross subject to netting	4	5
Level 2 | Price Risk Derivative, Gas
Assets:
Price risk management instruments, gross subject to netting	3	1
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	192	203
TOTAL ASSETS	192	203
Liabilities:
TOTAL LIABILITIES	83	108
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	192	203
Liabilities:
Price risk management instruments, gross subject to netting	83	108
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
Fair Value Measured at Net Asset Value | Nuclear decommissioning trusts
Assets:
Assets measured at NAV	19	16
Fair Value Measured at Net Asset Value | Long-term disability trust
Assets:
Assets measured at NAV	$ 142	$ 155