PENSION AND OTHER POSTRETIREMENT BENEFITS - Strategic Target Asset Allocation (Details)	Jun. 30, 2017
Minimum | Equity investments
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (percent)	45.00%
Minimum | Fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (percent)	20.00%
Minimum | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (percent)	5.00%
Minimum | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (percent)	0.00%
Maximum | Equity investments
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (percent)	75.00%
Maximum | Fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (percent)	42.00%
Maximum | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (percent)	15.00%
Maximum | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (percent)	10.00%