SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	$ 110	$ 128	$ 332	$ 385
Interest cost	189	171	568	515
Expected return on plan assets	(226)	(255)	(679)	(766)
Amortization of prior service cost	(1)	(1)	(4)	(4)
Amortization of net actuarial loss	1	1	2	4
Net periodic benefit cost	73	44	219	134
Regulatory account transfer	10	41	31	118
Total	83	85	250	252
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	14	16	42	49
Interest cost	19	17	57	52
Expected return on plan assets	(31)	(33)	(92)	(98)
Amortization of prior service cost	3	4	10	11
Amortization of net actuarial loss	0	(1)	(2)	(4)
Net periodic benefit cost	5	3	15	10
Regulatory account transfer	0	0	0	0
Total	$ 5	$ 3	$ 15	$ 10