Employee Future Benefits - Defined Benefit Obligation (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligation, beginning of period	$ 240
Defined benefit obligation, ending of period	158	$ 240
Present value of defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligation, beginning of period	593
Defined benefit obligation, ending of period	447	593
Registered
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligation, beginning of period	130
Defined benefit obligation, ending of period	71	130
Registered \| Present value of defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligation, beginning of period	469	542
Current service cost	1	3
Interest cost	13	12
Benefits paid	(57)	(54)
Curtailment		(7)
Actuarial gain arising from financial assumptions	(83)	(26)
Actuarial loss (gain) arising from experience adjustments	1	(1)
Change in foreign exchange rates	1
Defined benefit obligation, ending of period	345	469
Supplemental
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligation, beginning of period	87
Defined benefit obligation, ending of period	70	87
Supplemental \| Present value of defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligation, beginning of period	101	109
Current service cost	1	2
Interest cost	3	2
Benefits paid	(5)	(5)
Curtailment		0
Actuarial gain arising from financial assumptions	(22)	(7)
Actuarial loss (gain) arising from experience adjustments	7	0
Change in foreign exchange rates	0
Defined benefit obligation, ending of period	85	101
Other
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligation, beginning of period	23
Defined benefit obligation, ending of period	17	23
Other \| Present value of defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligation, beginning of period	23	24
Current service cost	0	1
Interest cost	0	0
Benefits paid	1	(1)
Curtailment		0
Actuarial gain arising from financial assumptions	(5)	(1)
Actuarial loss (gain) arising from experience adjustments	(2)	0
Change in foreign exchange rates	0
Defined benefit obligation, ending of period	17	23
Total \| Present value of defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligation, beginning of period	593	675
Current service cost	2	6
Interest cost	16	14
Benefits paid	(61)	(60)
Curtailment		(7)
Actuarial gain arising from financial assumptions	(110)	(34)
Actuarial loss (gain) arising from experience adjustments	6	(1)
Change in foreign exchange rates	1
Defined benefit obligation, ending of period	$ 447	$ 593

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions that result in remeasurements of the net defined benefit liability (asset). Financial assumptions deal with items such as: (a) the discount rate; (b) benefit levels, excluding any cost of the benefits to be met by employees, and future salary; (c) in the case of medical benefits, future medical costs, including claim handling costs (ie the costs that will be incurred in processing and resolving claims, including legal and adjuster's fees); and (d) taxes payable by the plan on contributions relating to service before the reporting date or on benefits resulting from that service. [Refer: Net defined benefit liability (asset)]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2022-03-24
-Paragraph 141
-Subparagraph c
-Clause iii
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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from employee service in the current period. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2022-03-24
-Paragraph 141
-Subparagraph a
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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

+ References

No definition available.

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- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from the gain (loss) on changes in the effect of limiting a net defined benefit asset to the asset ceiling, excluding amounts included in interest income or expense. [Refer: Interest income (expense); Net defined benefit liability (asset); Increase (decrease) in net defined benefit liability (asset) resulting from interest expense (income)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2022-03-24
-Paragraph 141
-Subparagraph c
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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from changes in foreign exchange rates. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2022-03-24
-Paragraph 141
-Subparagraph e
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-URIDate 2022-03-24

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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from the passage of time. [Refer: Interest expense; Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2022-03-24
-Paragraph 141
-Subparagraph b
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- Definition

The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2022-03-24
-Paragraph 140
-Subparagraph a
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- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan in respect of settlements. [Refer: Decrease (increase) in net defined benefit liability (asset) resulting from gains (losses) arising from settlements; Net defined benefit liability (asset); Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2022-03-24
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-URIDate 2022-03-24

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- Definition

Curtailment and Plan Amendment Gain (Loss), Net Defined Benefit Liability (Asset)

+ References

No definition available.

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