SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	$ 132	$ 111
Interest cost	178	189
Expected return on plan assets	(261)	(227)
Amortization of prior service cost	(1)	(1)
Amortization of net actuarial loss	1	1
Net periodic benefit cost	49	73
Regulatory account transfer	34	10
Total	83	83
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	15	14
Interest cost	16	19
Expected return on plan assets	(34)	(31)
Amortization of prior service cost	3	4
Amortization of net actuarial loss	(5)	(1)
Net periodic benefit cost	(5)	5
Regulatory account transfer	0	0
Total	$ (5)	$ 5