EMPLOYEE BENEFITS - Schedule of Assumptions used To Calculate Pension and SERP and PBOP (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return	7.00%	7.00%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return		8.25%	8.25%
Compensation/Progression Rate		3.50%	3.50%
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return		8.25%	8.25%
Minimum | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.63%	3.85%	3.20%
Expected Long-Term Rate of Return	8.25%
Compensation/Progression Rate	3.50%
Minimum | Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.85%	3.28%	3.48%
Expected Long-Term Rate of Return	8.25%
Maximum | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.55%	4.62%	3.90%
Compensation/Progression Rate	4.00%	4.00%
Maximum | Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.65%	3.94%	4.64%