PENSION AND OTHER POSTRETIREMENT BENEFITS - PLAN ASSETS (Details) - Pension Benefits	Dec. 31, 2020 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Required capitalization for plan asset allocation (less than)	$ 250,000,000.0
Required capitalization for plan asset allocation, small cap (as low as)	$ 50,000,000.0
Minimum | U.S equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation (as a percent)	40.00%
Minimum | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation (as a percent)	10.00%
Minimum | Fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation (as a percent)	25.00%
Minimum | Other investments
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation (as a percent)	0.00%
Maximum | U.S equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation (as a percent)	70.00%
Maximum | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation (as a percent)	25.00%
Maximum | Fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation (as a percent)	60.00%
Maximum | Other investments
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation (as a percent)	20.00%