Pension Plans and Other Post-Retirement Benefits - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 CAD ($) Year	Dec. 31, 2018 CAD ($)
Disclosure of defined benefit plans [line items]
Age requirement \| Year	50
Requisite service period	10 years
Equity investments	3.00%	3.00%
Post-employment benefit expense, defined contribution plans \| $	$ 131	$ 120
Fixed income investments \| Level 1
Disclosure of defined benefit plans [line items]
Equity investments	3.00%	2.00%

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 2019-01-01
-Paragraph 53
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_53&doctype=Standard
-URIDate 2019-03-27

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