EMPLOYEE BENEFITS - TARGET ASSET ALLOCATIONS (Details)	Dec. 31, 2020
Pension Plan | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations (as a percent)	45.00%
Pension Plan | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations (as a percent)	45.00%
Pension Plan | Private equity and real estate
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations (as a percent)	10.00%
OPEB Plan | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations (as a percent)	45.00%
OPEB Plan | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations (as a percent)	55.00%