PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Assumptions We Use in Estimating Health Care Benefit Costs (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
U.S.
Defined Benefit Plan Disclosure [Line Items]
Rate that the cost trend rate gradually declines to	4.50%	4.50%
Year the cost trend rate is reached	2037	2037
U.S. | Health Reimbursement Account [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted health care cost trend rate assumed for next year	4.50%
U.S. | Pre Medicare [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted health care cost trend rate assumed for next year	8.90%
Canada
Defined Benefit Plan Disclosure [Line Items]
Weighted health care cost trend rate assumed for next year	4.90%
Rate that the cost trend rate gradually declines to	4.30%	4.30%
Year the cost trend rate is reached	2028	2028
Next year [Member] | U.S. | Health Reimbursement Account [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted health care cost trend rate assumed for next year	4.50%	4.50%
Next year [Member] | U.S. | Pre Medicare [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted health care cost trend rate assumed for next year	8.40%	8.90%
Next year [Member] | Canada
Defined Benefit Plan Disclosure [Line Items]
Weighted health care cost trend rate assumed for next year	5.10%	4.90%