EMPLOYEE BENEFIT PLANS (Schedule of Assumptions Used in Calculating Projected Benefit Cost and Net Periodic Benefit Cost) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets	9.60%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.77%	3.46%	4.35%
Rate of future compensation increases	3.80%	3.90%	3.90%
Expected return on plan assets	5.10%	5.70%	6.00%
Interest crediting rate for cash balance plan	1.95%	2.11%	3.15%
PBOP Plans | Minimum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.67%	3.37%	4.29%
Expected return on plan assets	3.10%	3.50%	3.60%
PBOP Plans | Maximum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.80%	3.47%	4.37%
Expected return on plan assets	6.10%	6.60%	6.80%