EQUITY - Schedule Using Black-Scholes Module (Details)	12 Months Ended
Dec. 31, 2020 USD ($) yr $ / shares	Dec. 31, 2019 USD ($) yr $ / shares	Dec. 31, 2020 CAD ($)	Dec. 31, 2019 CAD ($)
Management Share Option Plan \| Equity-Settled Share-Based Payment Arrangement
Disclosure of terms and conditions of share-based payment arrangement [line items]
Weighted average share price, share options granted \| $ / shares	$ 45.21	$ 30.42
Weighted-average fair value of a unit	$ 5.54	$ 3.92
Average term to exercise \| yr	7.5	7.5
Expected volatility, share options granted	17.00%	16.90%
Liquidity discount	25.00%	25.00%
Expected dividend as percentage, share options granted	1.50%	2.00%
Risk free interest rate, share options granted	1.40%	2.50%
Escrowed Stock Plan \| Equity-Settled Share-Based Payment Arrangement
Disclosure of terms and conditions of share-based payment arrangement [line items]
Weighted average share price, share options granted \| $ / shares	$ 45.21	$ 34.08
Weighted-average fair value of a unit	$ 5.54	$ 4.54
Average term to exercise \| yr	7.5	8,500,000
Expected volatility, share options granted	17.00%	17.30%
Liquidity discount	25.00%	25.00%
Expected dividend as percentage, share options granted	1.50%	1.80%
Risk free interest rate, share options granted	1.40%	2.10%
Deferred Stock Unit \| Cash-Settled Share-Based Payment Arrangement
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share Price on Date of Remeasurement in Canadian Dollars Per Share			$ 52.62	$ 50.02
Share price, on date of measurement	$ 41.27	$ 38.53

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- Definition

Share Price on Date of Remeasurement in Canadian Dollars Per Share

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- Definition

Share Price on Date of Remeasurement in US Dollars per Share

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- Definition

The expected volatility of the share price used to calculate the fair value of the share options granted. Expected volatility is a measure of the amount by which a price is expected to fluctuate during a period. The measure of volatility used in option pricing models is the annualised standard deviation of the continuously compounded rates of return on the share over a period of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
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- Definition

The option life of share options granted.

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The implied yield currently available on zero-coupon government issues of the country in whose currency the exercise price for share options granted is expressed, with a remaining term equal to the expected term of the option being valued (based on the option's remaining contractual life and taking into account the effects of expected early exercise). [Refer: Government [member]]

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- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

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- Definition

The percentage of an expected dividend used to calculate the fair value of share options granted.

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- Definition

The weighted average fair value of share options granted during the period at the measurement date. [Refer: Weighted average [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
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- Definition

The weighted average share price used as input to the option pricing model to calculate the fair value of share options granted. [Refer: Option pricing model [member]; Weighted average [member]]

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