PENSION AND OTHER POSTRETIREMENT BENEFITS - AMOUNT RECOGNIZED IN ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - CAD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Canada \| Pension
Amount included in AOCI
Net actuarial loss (gain)	$ 445	$ 435
Prior service credit	0	0
Total amount recognized in AOCI	445	435
Canada \| OPEB
Amount included in AOCI
Net actuarial loss (gain)	(7)	(29)
Prior service credit	(1)	(2)
Total amount recognized in AOCI	(8)	(31)
United States \| Pension
Amount included in AOCI
Net actuarial loss (gain)	134	133
Prior service credit	(2)	(3)
Total amount recognized in AOCI	132	130
United States \| OPEB
Amount included in AOCI
Net actuarial loss (gain)	(23)	(15)
Prior service credit	(13)	(15)
Total amount recognized in AOCI	$ (36)	$ (30)

Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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-Publisher FASB
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-SubTopic 10
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Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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- Definition

Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

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