SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	$ 133	$ 110	$ 397	$ 332
Interest cost	178	189	535	568
Expected return on plan assets	(261)	(226)	(783)	(679)
Amortization of prior service cost	(1)	(1)	(4)	(4)
Amortization of net actuarial loss	1	1	3	2
Net periodic benefit cost	50	73	148	219
Regulatory account transfer	34	10	102	31
Total	84	83	250	250
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	15	14	46	42
Interest cost	16	19	47	57
Expected return on plan assets	(34)	(31)	(103)	(92)
Amortization of prior service cost	3	3	10	10
Amortization of net actuarial loss	(5)	0	(15)	(2)
Net periodic benefit cost	(5)	5	(15)	15
Regulatory account transfer	0	0	0	0
Total	$ (5)	$ 5	$ (15)	$ 15