SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	$ 147	$ 133	$ 440	$ 397
Interest cost	161	178	484	535
Expected return on plan assets	(261)	(261)	(784)	(783)
Amortization of prior service cost	(1)	(1)	(4)	(4)
Amortization of net actuarial loss	1	1	4	3
Net periodic benefit cost	47	50	140	148
Regulatory account transfer	37	34	111	102
Total	84	84	251	250
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	15	15	47	46
Interest cost	13	16	39	47
Expected return on plan assets	(33)	(34)	(103)	(103)
Amortization of prior service cost	3	3	10	10
Amortization of net actuarial loss	(8)	(5)	(24)	(15)
Net periodic benefit cost	(10)	(5)	(31)	(15)
Regulatory account transfer	0	0	0	0
Total	$ (10)	$ (5)	$ (31)	$ (15)