INCOME TAXES - UNRECOGNIZED TAX BENEFITS (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
UNRECOGNIZED TAX BENEFITS
Unrecognized tax benefits at beginning of year	$ 139	$ 150
Gross increases for tax positions of current year	1	2
Gross decreases for tax positions of prior year	(1)	(12)
Change in translation of foreign currency	(4)	3
Lapses of statute of limitations	(6)	(3)
Settlements	0	(1)
Unrecognized tax benefits at end of year	129	139
Interest and penalties expense (recovery) related to unrecognized tax benefits	3	5
Accrued interest and penalties related to unrecognized tax benefits	$ 15	$ 12

Amount of increase (decrease) in unrecognized tax benefits resulting from foreign currency translation.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

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- Definition

Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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- Definition

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

+ References

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Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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