Impairment Of Long-Lived Assets To Be Disposed Of, Pre-Tax

No definition available.

Name:	cni_ImpairmentOfLongLivedAssetsToBeDisposedOfPreTax
Namespace Prefix:	cni_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The aggregate amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482130/360-10-45-15

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

+ Details

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Balance Type:	debit
Period Type:	instant

- Details

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- Details

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- Details

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Assets held for sale (Details) - CAD ($) $ in Millions		12 Months Ended
Assets held for sale (Details) - CAD ($) $ in Millions	May 08, 2024	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Nov. 12, 2024
Long Lived Assets Held-for-sale [Line Items]
Loss on assets held for sale		$ 0	$ 78	$ 0
Operating lease right-of-use assets		440	$ 485
Operating lease liability		$ 424
Track and Roadway
Long Lived Assets Held-for-sale [Line Items]
Operating lease right-of-use assets					$ 124
Operating lease liability					$ 124
Disposal Group, Held-for-sale, Not Discontinued Operations \| Track and Roadway
Long Lived Assets Held-for-sale [Line Items]
Impairment loss, pre-tax	$ 78
Loss on assets held for sale	$ 58