The amount of funds to be distributed to those claiming derailment damages.

No definition available.

Name:	cp_AmountofFundDistributed
Namespace Prefix:	cp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Long term purchase commitment period beginning year.

+ References

No definition available.

+ Details

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Namespace Prefix:	cp_
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- Definition

Long term purchase commitment period ending year.

+ References

No definition available.

+ Details

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- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

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

- Definition

The minimum amount the entity agreed to spend under the long-term purchase commitment.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

+ Details

Name:	us-gaap_LossContingencyPendingClaimsNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

+ Details

Name:	us-gaap_PurchaseObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cp_IrvingOilMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cp_QuebecMinisterofSustainableDevelopmentandEnvironmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cp_QuebecAttorneyGeneralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cp_InitialInsurerClaimantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=cp_SubrogatedInsuranceClaimMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cp_AdditionalInsurerClaimantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cp_TheWDTrusteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=cp_LadingLossRecoveryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=cp_MontrealMaineandAtlanticRailwayBankruptcyEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cp_WorldFuelEntitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=cp_OperatingExpendituresMember
Namespace Prefix:
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Commitments and Contingencies - Narrative (Details) CAD in Millions								12 Months Ended
	Dec. 28, 2017 CAD	Oct. 10, 2017 CAD	Jul. 11, 2016 CAD claim	Jul. 05, 2016 CAD	Jul. 04, 2016 CAD claim	Apr. 12, 2016 CAD	Jul. 06, 2015 CAD	Dec. 31, 2017 CAD	Dec. 31, 2016 CAD	Dec. 31, 2015 CAD
Commitments and Contingencies [Line Items]
Period for which future capital and operating expenditures are committed, beginning year								2018
Period for which future capital and operating expenditures are committed, end year								2032
Estimated future purchase commitment								CAD 1,400
Total minimum lease payments								351
Expenses for operating leases								104	CAD 111	CAD 127
Lac-Megantic Rail Incident \| Claimed damages as a result of derailment
Commitments and Contingencies [Line Items]
Amount of fund distributed								440
Lac-Megantic Rail Incident \| Irving Oil [Member]
Commitments and Contingencies [Line Items]
Value of damages sought						CAD 60
Lac-Megantic Rail Incident \| Quebec Minister of Sustainable Development, Environment, Wildlife and Parks
Commitments and Contingencies [Line Items]
Value of damages sought				CAD 95
Lac-Megantic Rail Incident \| Quebec Attorney General
Commitments and Contingencies [Line Items]
Value of damages sought		CAD 315					CAD 409
Lac-Megantic Rail Incident \| Initial Insurer Claimants \| Subrogated insurance claim
Commitments and Contingencies [Line Items]
Value of damages sought	CAD 14				CAD 16
Number of subrogated insurers \| claim					8
Lac-Megantic Rail Incident \| Additional Insurer Claimants \| Subrogated insurance claim
Commitments and Contingencies [Line Items]
Value of damages sought			CAD 3
Number of subrogated insurers \| claim			2
Lac-Megantic Rail Incident \| The WD Trustee \| Damaged railcars loss recovery
Commitments and Contingencies [Line Items]
Value of damages sought						6
Lac-Megantic Rail Incident \| Montreal Maine and Atlantic Railway \| World Fuel Entities [Member]
Commitments and Contingencies [Line Items]
Value of damages sought						CAD 110
Capital Expenditure [Member]
Commitments and Contingencies [Line Items]
Total future committed expenditure								632
Operating Expenditures [Member]
Commitments and Contingencies [Line Items]
Total future committed expenditure								CAD 1,700