EMPLOYEE BENEFIT PLANS (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) noncallable_bond	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Assumed health care cost trend rate	6.30%
Ultimate trend rate	4.50%
Assumed return	5.10%
10 year actual rate of return	9.60%
Number of Aa-grade non-callable bonds used to develop the yield curve for rate used (noncallable bond) | noncallable_bond	835
Total fair value of trust other net liabilities	$ (249)	$ 99
Retirement savings plan expense	$ 119	$ 109	$ 105
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
10 year actual rate of return	5.10%	5.70%	6.00%
Company contributions	$ 343	$ 328
Expected employer contribution next year	327
PBOP Plans
Defined Benefit Plan Disclosure [Line Items]
Company contributions	26	$ 29
Expected employer contribution next year	$ 15