employee future benefits - Defined contribution pension plans expense (Details) - CAD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
employee future benefits
Union pension plan and public service pension plan contributions	$ 3	$ 4	$ 6	$ 8
Other defined contribution pension plans	29	31	53	55
Total	$ 32	$ 35	$ 59	$ 63

The amount of post-employment benefit expense relating to defined contribution plans. Defined contribution plans are post-employment benefit plans under which an entity pays fixed contributions into a separate entity (a fund) and will have no legal or constructive obligation to pay further contributions if the fund does not hold sufficient assets to pay all employee benefits relating to employee service in the current and prior periods.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2023-01-01
-Paragraph 53
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_53&doctype=Standard
-URIDate 2023-03-23

Name:	ifrs-full_PostemploymentBenefitExpenseDefinedContributionPlans
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration