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Employee Future Benefits - Fair Value of Plan Assets by Major Category (Details) - CAD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Disclosure of fair value of plan assets [line items] |  |
Loans(1) | $ 2 | $ 2
Alternative funds | 44 | 39
Money market and cash and cash equivalents | 21 | 20
Total | 284 | 289
Canadian |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 12 | 18
US |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 6 | 17
International |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 86 | 79
Private |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 1 | 1
A - AAA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 92 | 88
BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 16 | 19
Loans(1) |  | 1
Below BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 4 | 6
A |  |
Disclosure of fair value of plan assets [line items] |  |
Loans(1) | 1 | 1
Level I |  |
Disclosure of fair value of plan assets [line items] |  |
Loans(1) | 0 | 0
Alternative funds | 0 | 0
Money market and cash and cash equivalents | 2 | 0
Total | 3 | 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 | 0 | 0
Level I | Private |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 0 | 0
Level I | A - AAA |  |
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] |  |
Loans(1) | 2 | 2
Alternative funds | 0 | 0
Money market and cash and cash equivalents | 19 | 20
Total | 160 | 169
Level II | Canadian |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 12 | 18
Level II | US |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 6 | 17
Level II | International |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 86 | 79
Level II | Private |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 0 | 0
Level II | A - AAA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 30 | 27
Level II | BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 5 | 6
Level II | Below BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 0 | 0
Level III |  |
Disclosure of fair value of plan assets [line items] |  |
Loans(1) | 0 | 0
Alternative funds | 44 | 39
Money market and cash and cash equivalents | 0 | 0
Total | 121 | 119
Level III | Canadian |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 0 | 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 |  |
Disclosure of fair value of plan assets [line items] |  |
Equity securities | 1 | 1
Level III | A - AAA |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 62 | 61
Level III | BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | 10 | 12
Level III | Below BBB |  |
Disclosure of fair value of plan assets [line items] |  |
Bonds | $ 4 | $ 6

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