Other Long-Term Liabilities - Weighted Average Assumptions Used to Calculate Share-Based Compensation Liability (Details)	12 Months Ended
Dec. 31, 2020 CAD ($) year $ / shares	Dec. 31, 2019 CAD ($) year $ / shares	Dec. 31, 2018 CAD ($) year $ / shares
Disclosure of terms and conditions of share-based payment arrangement [line items]
Fair value	$ 3.47	$ 7.88	$ 3.33
Share price \| $ / shares	$ 30.59	$ 42.00	$ 32.94
Expected volatility	39.80%	26.70%	27.40%
Expected dividend yield	5.60%	3.60%	4.10%
Risk free interest rate	0.30%	1.70%	1.90%
Expected forfeiture rate	4.30%	4.30%	4.20%
Stock options
Disclosure of terms and conditions of share-based payment arrangement [line items]
Expected stock option life \| year	4.3	4.4	4.4
Intrinsic value of vested stock options	$ 11,000,000	$ 75,000,000	$ 27,000,000

Expected Forfeiture As Percentage, Share Options Granted

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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
-Number 2
-IssueDate 2020-01-01
-Paragraph 47
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_47_a_i&doctype=Standard
-URIDate 2020-01-01

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- Definition

The option life of share options granted.

+ References

+ Details

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- Definition

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]]

+ References

+ Details

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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.

+ References

No definition available.

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- Definition

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

+ References

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- Definition

The intrinsic value of liabilities arising from share-based transactions for which the counterparty's right to cash or other assets had vested by the end of the period (for example, vested share appreciation rights). The intrinsic value is the difference between the fair value of the shares to which the counterparty has the (conditional or unconditional) right to subscribe, or which it has the right to receive, and the price (if any) that the counterparty is (or will be) required to pay for those shares. Share-based payment transactions are transactions in which the entity: (a) receives goods or services from the supplier of those goods or services (including an employee) in a share-based payment arrangement; or (b) incurs an obligation to settle the transaction with the supplier in a share-based payment arrangement when another group entity receives those goods or services, for which the counterparty's right to cash or other assets had vested by the end of the period (for example, vested share appreciation rights).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 51
-Subparagraph b
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_51_b_ii&doctype=Standard
-URIDate 2020-01-01

+ Details

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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
-IssueDate 2020-01-01
-Paragraph 47
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_47_a&doctype=Standard
-URIDate 2020-01-01

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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]]

+ References

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