SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	$ 132	$ 111	$ 264	$ 222
Interest cost	179	190	357	379
Expected return on plan assets	(261)	(226)	(522)	(453)
Amortization of prior service cost	(2)	(2)	(3)	(3)
Amortization of net actuarial loss	1	0	2	1
Net periodic benefit cost	49	73	98	146
Regulatory account transfer	34	10	68	21
Total	83	83	166	167
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	16	14	31	28
Interest cost	15	19	31	38
Expected return on plan assets	(35)	(30)	(69)	(61)
Amortization of prior service cost	4	3	7	7
Amortization of net actuarial loss	(5)	(1)	(10)	(2)
Net periodic benefit cost	(5)	5	(10)	10
Regulatory account transfer	0	0	0	0
Total	$ (5)	$ 5	$ (10)	$ 10