Goodwill - Movements in goodwill (Details) - Goodwill $ in Thousands	12 Months Ended
Sep. 30, 2023 CAD ($)
Reconciliation of changes in goodwill [abstract]
Beginning balance	$ 8,481,456
Business acquisitions	20,934
Foreign currency translation adjustment	222,060
Ending balance	8,724,450
Western and Southern Europe
Reconciliation of changes in goodwill [abstract]
Beginning balance	1,440,019
Business acquisitions	21,001
Foreign currency translation adjustment	94,710
Ending balance	1,555,730
U.S. Commercial and State Government
Reconciliation of changes in goodwill [abstract]
Beginning balance	1,278,176
Business acquisitions	0
Foreign currency translation adjustment	(19,799)
Ending balance	1,258,377
Canada
Reconciliation of changes in goodwill [abstract]
Beginning balance	1,142,148
Business acquisitions	0
Foreign currency translation adjustment	0
Ending balance	1,142,148
U.S. Federal
Reconciliation of changes in goodwill [abstract]
Beginning balance	1,108,267
Business acquisitions	0
Foreign currency translation adjustment	(17,564)
Ending balance	1,090,703
Scandinavia and Central Europe
Reconciliation of changes in goodwill [abstract]
Beginning balance	1,345,346
Business acquisitions	0
Foreign currency translation adjustment	37,970
Ending balance	1,383,316
U.K. and Australia
Reconciliation of changes in goodwill [abstract]
Beginning balance	834,960
Business acquisitions	(67)
Foreign currency translation adjustment	61,916
Ending balance	896,809
Finland, Poland and Baltics
Reconciliation of changes in goodwill [abstract]
Beginning balance	567,628
Business acquisitions	0
Foreign currency translation adjustment	37,257
Ending balance	604,885
Northwest and Central-East Europe
Reconciliation of changes in goodwill [abstract]
Beginning balance	501,307
Business acquisitions	0
Foreign currency translation adjustment	30,822
Ending balance	532,129
Asia Pacific
Reconciliation of changes in goodwill [abstract]
Beginning balance	263,605
Business acquisitions	0
Foreign currency translation adjustment	(3,252)
Ending balance	$ 260,353

The increase in intangible assets and goodwill resulting from acquisitions through business combinations. [Refer: Business combinations [member]; Intangible assets and goodwill]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 38
-IssueDate 2023-01-01
-Paragraph 118
-Subparagraph e
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- Definition

The increase (decrease) in intangible assets and goodwill resulting from the net exchange differences arising when the financial statements are translated from the functional currency into a different presentation currency, including the translation of a foreign operation into the presentation currency of the reporting entity. [Refer: Intangible assets and goodwill]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 38
-IssueDate 2023-01-01
-Paragraph 118
-Subparagraph e
-Clause vii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=38&code=ifrs-tx-2023-en-r&anchor=para_118_e_vii&doctype=Standard
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- Definition

The amount of intangible assets and goodwill held by the entity. [Refer: Goodwill; Intangible assets other than goodwill]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-IssueDate 2023-01-01
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