Financial and capital management - Change in Allowance for Doubtful Accounts (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Trade receivables
Reconciliation of changes in allowance account for credit losses of financial assets [abstract]
Balance, January 1	$ (149)	$ (62)
Additions	(83)	(134)
Usage and reversals	96	47
Balance, December 31	(136)	(149)
Contract assets
Reconciliation of changes in allowance account for credit losses of financial assets [abstract]
Balance, January 1	(59)	(68)
Additions	(9)	(31)
Usage and reversals	48	40
Balance, December 31	(20)	(59)
Current contract assets
Reconciliation of changes in allowance account for credit losses of financial assets [abstract]
Balance, January 1	(29)
Balance, December 31	(6)	(29)
Noncurrent contract assets
Reconciliation of changes in allowance account for credit losses of financial assets [abstract]
Balance, January 1	(30)
Balance, December 31	$ (14)	$ (30)

The amount of additional allowance for credit losses of financial assets recognised in profit or loss. [Refer: Allowance account for credit losses of financial assets]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2023-01-01
-Name IFRS
-Number 7
-IssueDate 2021-01-01
-Paragraph 16
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2017-en-b&anchor=para_16&doctype=Standard&book=b
-URIDate 2021-03-24

+ Details

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- Definition

The amount of an allowance account used to record impairments to financial assets due to credit losses. [Refer: Financial assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2023-01-01
-Name IFRS
-Number 7
-IssueDate 2021-01-01
-Paragraph 16
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2017-en-b&anchor=para_16&doctype=Standard&book=b
-URIDate 2021-03-24

+ Details

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- References

No definition available.

+ Details

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- Definition

The decrease in an allowance account for credit losses of financial assets resulting from the utilisation of the allowance. [Refer: Allowance account for credit losses of financial assets]

+ References

+ Details

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