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Employee Future Benefits - Fair Value of Plan Assets by Major Category (Details) - CAD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Disclosure of fair value of plan assets [line items] |  |
Money market and cash and cash equivalents | $ 20 | $ 19
Total | 353 | 381
Canadian |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 33 | 64
US |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 20 | 30
International |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 126 | 103
Private [Member] |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 1 | 1
AAA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 28 | 36
AA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 54 | 67
A |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 36 | 34
BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 25 | 23
Below BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 10 | 4
Level I |  |
Disclosure of fair value of plan assets [line items] |  |
Money market and cash and cash equivalents | 0 | 0
Total | 48 | 1
Level I | Canadian |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 0 | 0
Level I | US |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 0 | 0
Level I | International |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 47 | 0
Level I | Private [Member] |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 0 | 0
Level I | AAA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 0 | 0
Level I | AA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 0 | 0
Level I | A |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 0 | 0
Level I | BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 1 | 1
Level I | Below BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 0 | 0
Level II |  |
Disclosure of fair value of plan assets [line items] |  |
Money market and cash and cash equivalents | 20 | 19
Total | 300 | 379
Level II | Canadian |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 29 | 64
Level II | US |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 20 | 30
Level II | International |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 79 | 103
Level II | Private [Member] |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 0 | 0
Level II | AAA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 28 | 36
Level II | AA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 54 | 67
Level II | A |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 36 | 34
Level II | BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 24 | 22
Level II | Below BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 10 | 4
Level III |  |
Disclosure of fair value of plan assets [line items] |  |
Money market and cash and cash equivalents | 0 | 0
Total | 5 | 1
Level III | Canadian |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 4 | 0
Level III | US |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 0 | 0
Level III | International |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 0 | 0
Level III | Private [Member] |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 1 | 1
Level III | AAA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 0 | 0
Level III | AA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 0 | 0
Level III | A |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 0 | 0
Level III | BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 0 | 0
Level III | Below BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | $ 0 | $ 0

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- Definition The amount instruments representing debt (rather than equity) contribute to the fair value of defined benefit plan assets. [Refer: Plan assets, at fair value; Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Name IAS -Number 19 -IssueDate 2021-01-01 -Paragraph 142 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2021-en-r&anchor=para_142_c&doctype=Standard -URIDate 2021-03-24 + Details
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