PENSION AND OTHER POST-EMPLOYMENT BENEFIT PLANS - Assets Within Our U.S. and Canadian Qualified and Registered Pension Plans (Details) - Qualified and Registered Plans	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	100.00%	100.00%
Cash and short-term investments
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	3.60%	3.20%
Fixed income investments, Corporate
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	30.60%	33.90%
Fixed income investments, Government
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	31.80%	25.40%
Fixed Income Investments, Repurchase Agreements
Defined Benefit Plan Disclosure [Line Items]
Repurchase agreements	(2.80%)	(4.70%)
Public equity investments
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	0.00%	0.10%
Hedge funds and related investments
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	6.90%	14.30%
Private equity and related investments
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	30.00%	27.70%
Derivative instruments, net
Defined Benefit Plan Disclosure [Line Items]
Assets invested in pension plan, allocation percentage	0.20%	0.30%
Accrued liabilities
Defined Benefit Plan Disclosure [Line Items]
Repurchase agreements	(0.30%)	(0.20%)