Intangible Assets - Schedule of Intangible Assets (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	$ 265.7
Ending balance	427.0	$ 265.7
Cost
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	540.5	610.7
Additions	84.4	13.7
Additions arising on acquisitions	183.8	37.6
Removal of fully amortized assets	(68.8)	(112.6)
Impact of foreign exchange	33.6	(8.9)
Ending balance	773.5	540.5
Accumulated depreciation
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	(274.8)	(290.3)
Amortization	123.8	102.0
Removal of fully amortized assets	68.8	112.6
Impact of foreign exchange	16.7	(4.9)
Ending balance	(346.5)	(274.8)
Client Relationships
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	231.4
Ending balance	326.2	231.4
Client Relationships \| Cost
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	464.1	471.9
Additions	0.0	0.0
Additions arising on acquisitions	137.7	25.2
Removal of fully amortized assets	(30.9)	(25.4)
Impact of foreign exchange	31.3	(7.6)
Ending balance	602.2	464.1
Client Relationships \| Accumulated depreciation
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	(232.7)	(215.6)
Amortization	58.5	46.3
Removal of fully amortized assets	30.9	25.4
Impact of foreign exchange	15.7	(3.8)
Ending balance	(276.0)	(232.7)
Contract Backlog
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	8.3
Ending balance	23.9	8.3
Contract Backlog \| Cost
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	12.4	48.6
Additions	0.0	0.0
Additions arising on acquisitions	45.8	12.4
Removal of fully amortized assets	(13.4)	(47.8)
Impact of foreign exchange	2.0	(0.8)
Ending balance	46.8	12.4
Contract Backlog \| Accumulated depreciation
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	(4.1)	(31.4)
Amortization	31.1	21.3
Removal of fully amortized assets	13.4	47.8
Impact of foreign exchange	1.1	(0.8)
Ending balance	(22.9)	(4.1)
Software and other
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	26.0
Ending balance	76.9	26.0
Software and other \| Cost
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	64.0	90.2
Additions	84.4	13.7
Additions arising on acquisitions	0.3	0.0
Removal of fully amortized assets	(24.5)	(39.4)
Impact of foreign exchange	0.3	(0.5)
Ending balance	124.5	64.0
Software and other \| Accumulated depreciation
Reconciliation of changes in intangible assets other than goodwill [abstract]
Beginning balance	(38.0)	(43.3)
Amortization	34.2	34.4
Removal of fully amortized assets	24.5	39.4
Impact of foreign exchange	(0.1)	(0.3)
Ending balance	$ (47.6)	$ (38.0)

The increase in intangible assets other than goodwill resulting from acquisitions through business combinations. [Refer: Total for all business combinations [member]; Intangible assets other than goodwill]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 38
-IssueDate 2024-01-01
-Paragraph 118
-Subparagraph e
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The amount of additions to intangible assets other than goodwill, other than those acquired through business combinations. [Refer: Total for all business combinations [member]; Intangible assets other than goodwill]

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The amount of amortisation of intangible assets other than goodwill. [Refer: Depreciation and amortisation expense; Intangible assets other than goodwill]

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 38
-IssueDate 2024-01-01
-Paragraph 118
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 38
-IssueDate 2024-01-01
-Paragraph 118
-Subparagraph e
-Clause vii
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The amount of identifiable non-monetary assets without physical substance. This amount does not include goodwill. [Refer: Goodwill]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 38
-IssueDate 2024-01-01
-Paragraph 118
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The decrease in intangible assets other than goodwill resulting from retirements. [Refer: Intangible assets other than goodwill]

+ References

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