Amount of fund to be distributed to those claiming derailment damages.

No definition available.

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

- Definition

Long term purchase commitment period.

+ References

No definition available.

+ Details

Name:	cp_LongTermPurchaseCommitmentPeriod
Namespace Prefix:	cp_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Loss Contingency, Damages Sought Previously, Value

+ References

No definition available.

+ Details

Name:	cp_LossContingencyDamagesSoughtPreviouslyValue
Namespace Prefix:	cp_
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

Name:	us-gaap_LongTermPurchaseCommitmentAmount
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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14557-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14435-108349

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14326-108349

+ Details

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

- Definition

Number of plaintiffs that have filed claims pertaining to a loss contingency.

+ References

No definition available.

+ Details

Name:	us-gaap_LossContingencyNumberOfPlaintiffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14435-108349

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
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

Name:	us-gaap_OtherCommitmentsLineItems
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

Commitments and Contingencies - Narrative (Details) - 12 months ended Dec. 31, 2020 $ in Millions, $ in Millions	CAD ($) claim	USD ($) claim
Commitments and Contingencies [Line Items]
Estimated future purchase commitment, next 5 years	$ 1,600
Minimum
Commitments and Contingencies [Line Items]
Period for which future capital and operating expenditures are committed	2021	2021
Maximum
Commitments and Contingencies [Line Items]
Period for which future capital and operating expenditures are committed	2032	2032
Lac-Megantic Rail Accident \| Claimed damages as a result of derailment
Commitments and Contingencies [Line Items]
Amount to be distributed	$ 440
Lac-Megantic Rail Accident \| Quebec Minister of Sustainable Development, Environment, Wildlife and Parks
Commitments and Contingencies [Line Items]
Value of damages sought	95
Lac-Megantic Rail Accident \| Attorney General of Quebec
Commitments and Contingencies [Line Items]
Value of damages sought	315
Damages Sought Previously, Value	409
Lac-Megantic Rail Accident \| Initial Subrogated Insurers \| Subrogated insurance claim
Commitments and Contingencies [Line Items]
Value of damages sought	15
Damages Sought Previously, Value	$ 16
Number of subrogated insurer claims \| claim	8
Lac-Megantic Rail Accident \| Additional Subrogated Insurers \| Subrogated insurance claim
Commitments and Contingencies [Line Items]
Value of damages sought	$ 3
Number of subrogated insurer claims \| claim	2
Lac-Megantic Rail Accident \| Class Action Plaintiffs
Commitments and Contingencies [Line Items]
Value of damages sought		$ 5
Number of plaintiffs \| claim	48	48
Lac-Megantic Rail Accident \| MMAR Estate Representative \| Damages for loss in business value
Commitments and Contingencies [Line Items]
Value of damages sought		$ 30
Lac-Megantic Rail Accident \| WD Trustee \| Damaged railcars and lost crude recovery
Commitments and Contingencies [Line Items]
Value of damages sought		6
Lac-Megantic Rail Accident \| WD Trustee \| Reimbursement for settlement paid by consignor
Commitments and Contingencies [Line Items]
Value of damages sought		110
Lac-Megantic Rail Accident \| WD Trustee \| Reimbursement for settlement paid by consignee
Commitments and Contingencies [Line Items]
Value of damages sought		$ 60
Capital Expenditures
Commitments and Contingencies [Line Items]
Future committed expenditures	$ 547
Operating Expenditures
Commitments and Contingencies [Line Items]
Future committed expenditures	$ 1,700