SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	$ 146	$ 132	$ 293	$ 264
Interest cost	162	179	323	357
Expected return on plan assets	(262)	(261)	(523)	(522)
Amortization of prior service cost	(2)	(2)	(3)	(3)
Amortization of net actuarial loss	2	1	3	2
Net periodic benefit cost	46	49	93	98
Regulatory account transfer	37	34	74	68
Total	83	83	167	166
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	16	16	32	31
Interest cost	13	15	26	31
Expected return on plan assets	(35)	(35)	(70)	(69)
Amortization of prior service cost	3	4	7	7
Amortization of net actuarial loss	(8)	(5)	(16)	(10)
Net periodic benefit cost	(11)	(5)	(21)	(10)
Regulatory account transfer	0	0	0	0
Total	$ (11)	$ (5)	$ (21)	$ (10)