Disposal Group, Not Discontinued Operation, Gain (Loss) On Disposal, Net Of Tax

No definition available.

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Balance Type:	credit
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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.

+ Details

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- Definition

Amount of gain (loss) on sale or disposal of property, plant and equipment assets, excluding oil and gas property and timber property.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2443-110228

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230

+ Details

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- Definition

The aggregate amount of gains or losses resulting from nonoperating activities (for example, interest and dividend revenue, property, plant and equipment impairment loss, and so forth).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7,9)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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Period Type:	duration

- Definition

The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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

- Definition

Amount of income (expense) related to nonoperating activities, classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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

- Definition

Amount of cash inflow for the sale of long-lived, physical assets used to produce goods and services and not intended for resale, classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

+ Details

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

- References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=cni_CentralStationRailwayMember
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- Details

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Other Income (Details) - CAD ($) $ in Millions					12 Months Ended
Other Income (Details) - CAD ($) $ in Millions	Nov. 15, 2018	Sep. 05, 2018	Apr. 09, 2018	Apr. 06, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Component of Other Income, Nonoperating [Abstract]
Gain on disposal of property					$ 0	$ 338	$ 0
Other					3	11	(10)
Total other income					53	376	12
Proceeds from Sale of Property, Plant, and Equipment [Abstract]
Disposal of property, cash proceeds					0	194	0
Property [Member]
Component of Other Income, Nonoperating [Abstract]
Gain on disposal of property					0	338	0
Land [Member]
Component of Other Income, Nonoperating [Abstract]
Gain on disposal of property					$ 50	$ 27	$ 22
Guelph [Member]
Proceeds from Sale of Property, Plant, and Equipment [Abstract]
Gain (loss) on sale of property	$ 79
Gain (loss) on disposal of property after-tax	$ 70
Doney And St-Francois Spurs [Member]
Proceeds from Sale of Property, Plant, and Equipment [Abstract]
Gain (loss) on sale of property		$ 36
Gain (loss) on disposal of property after-tax		32
Disposal of property, cash proceeds		$ 40
Central Station Railway [Member]
Proceeds from Sale of Property, Plant, and Equipment [Abstract]
Gain (loss) on sale of property			$ 184
Gain (loss) on disposal of property after-tax			156
Disposal of property, cash proceeds			$ 115
Calgary Industrial Lead [Member]
Proceeds from Sale of Property, Plant, and Equipment [Abstract]
Gain (loss) on sale of property				$ 39
Gain (loss) on disposal of property after-tax				34
Disposal of property, cash proceeds				$ 39