Properties - Capital Leases Included in Properties (Details) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finance Leased Assets [Line Items]
Cost	$ 310	$ 307
Accumulated depreciation	139	130
Net book value	171	177
Rolling stock
Finance Leased Assets [Line Items]
Cost	302	303
Accumulated depreciation	138	130
Net book value	164	173
Other
Finance Leased Assets [Line Items]
Cost	8	4
Accumulated depreciation	1	0
Net book value	$ 7	$ 4

Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services.

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121569800&loc=d3e45014-112735

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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 total gross amount less the charge for the use of the long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121616839&loc=d3e45280-112737

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- Definition

The total charge for the use of long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 2)
-URI http://asc.fasb.org/extlink&oid=121580752&loc=d3e38371-112697

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-Name Accounting Standards Codification
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-SubTopic 30
-Section 45
-Paragraph 1
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