Revenues (Disaggregated Revenue) (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 14,917	$ 14,321	$ 13,041
Remaining performance obligation	91
Freight [Member]
Disaggregation of Revenue [Line Items]
Revenues	14,198	13,548	12,293
Petroleum And Chemicals [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,052	2,660	2,208
Metals And Minerals [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,643	1,689	1,523
Forest Products [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,808	1,886	1,788
Coal [Member]
Disaggregation of Revenue [Line Items]
Revenues	658	661	535
Grain And Fertilizers [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,392	2,357	2,214
Intermodal [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,787	3,465	3,200
Automotive [Member]
Disaggregation of Revenue [Line Items]
Revenues	858	830	825
Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 719	$ 773	$ 748

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130556-203045

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