Business acquisition - Pro Forma Information (Details) $ in Millions		3 Months Ended	6 Months Ended
Apr. 13, 2023	Jun. 30, 2023 CAD ($)	Apr. 13, 2023	Jun. 30, 2022 CAD ($)	Jun. 30, 2023 CAD ($)	Jun. 30, 2022 CAD ($)
Business Acquisition [Line Items]
KCS historical, revenue		$ 164		$ 1,079	$ 1,351	$ 2,065
Pro forma CPKC, revenue		3,338		3,285	6,794	6,112
KCS historical, net income attributable to controlling shareholders		34		248	280	485
Pro forma, net income attributable to controlling shareholders		$ 615		$ 794	$ 1,371	$ 2,018
Canada, Dollars
Business Acquisition [Line Items]
Daily exchange rate used, revenue	1.35		1.35	1.28		1.27
Daily exchange rate used, net income			1.35			1.27

Business Acquisition, Foreign Currency Exchange Rate, Translation, Earnings

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- Definition

Business Acquisition, Foreign Currency Exchange Rate, Translation, Revenue

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
-URI https://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)
-URI https://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)
-URI https://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
-URI https://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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- Definition

This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)
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This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

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