SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	$ 111	$ 129	$ 222	$ 257
Interest cost	190	172	379	344
Expected return on plan assets	(226)	(256)	(453)	(511)
Amortization of prior service cost	(2)	(2)	(3)	(3)
Amortization of net actuarial loss	0	2	1	3
Net periodic benefit cost	73	45	146	90
Regulatory account transfer	10	39	21	77
Total	83	84	167	167
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	14	17	28	33
Interest cost	19	18	38	35
Expected return on plan assets	(30)	(32)	(61)	(65)
Amortization of prior service cost	3	3	7	7
Amortization of net actuarial loss	(1)	(2)	(2)	(3)
Net periodic benefit cost	5	4	10	7
Regulatory account transfer	0	0	0	0
Total	$ 5	$ 4	$ 10	$ 7