PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Rates We Use in Estimating Our Benefit Obligations (Details) - Pension	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Lump sum or installment distributions election	60.00%	60.00%
U.S.
Defined Benefit Plan Disclosure [Line Items]
Discount rates, benefit obligation	3.40%	4.40%
Canada
Defined Benefit Plan Disclosure [Line Items]
Discount rates, benefit obligation	3.10%	3.70%
Salaried \| Canada
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	3.25%	3.25%
Hourly \| Canada
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	3.00%	3.00%
Maximum \| Salaried \| U.S.
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	13.00%	13.00%
Maximum \| Hourly \| U.S.
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	13.00%	13.00%
Minimum \| Salaried \| U.S.
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	2.00%	2.00%
Minimum \| Hourly \| U.S.
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	2.30%	2.30%

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(1)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(2)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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The percentage that elected lump sum or installment distributions.

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