PENSION AND OTHER POSTRETIREMENT BENEFITS - PLAN ASSETS (Details) - Pension Benefits	Dec. 31, 2017 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	28.00%
Minimum | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation	13.00%
Minimum | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation	32.00%
Minimum | Other investments
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation	0.00%
Maximum | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation	48.00%
Maximum | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation	25.00%
Maximum | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation	42.00%
Maximum | Other investments
Defined Benefit Plan Disclosure [Line Items]
Target plan allocation	7.00%