EMPLOYEE BENEFIT PLANS (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	$ 530	$ 443	$ 514
Interest cost	713	758	687
Expected return on plan assets	(1,044)	(906)	(1,021)
Amortization of prior service cost	(6)	(6)	(6)
Amortization of net actuarial loss	3	3	5
Net periodic benefit cost	196	292	179
Less: transfer to regulatory account	136	42	157
Total expense recognized	332	334	336
PBOP Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	61	56	66
Interest cost	63	76	69
Expected return on plan assets	(138)	(123)	(130)
Amortization of prior service cost	14	14	14
Amortization of net actuarial loss	(21)	(3)	(5)
Net periodic benefit cost	$ (21)	$ 20	$ 14