Basis of calculating market related value of net periodic benefit cost.

No definition available.

Name:	cp_BasisOfCalculatingMarketRelatedValueOfNetPeriodicBenefitCost
Namespace Prefix:	cp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Real rate of return net of all fees and expenses related to long term investment strategy.

+ References

No definition available.

+ Details

Name:	cp_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRealRateOfReturnNetOfAllFeesAndExpensesRelatedToLongTermInvestmentStrategy
Namespace Prefix:	cp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Benefit Plan, Prior Period Gain (Loss)

+ References

No definition available.

+ Details

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

- Definition

Domestic Pension Plan as Percentage of Combined Pension Plan Assets

+ References

No definition available.

+ Details

Name:	cp_DomesticPensionPlanAsPercentageOfCombinedPensionPlanAssets
Namespace Prefix:	cp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Domestic Pension Plan as Percentage of Combined Pension Plan Obligations

+ References

No definition available.

+ Details

Name:	cp_DomesticPensionPlanAsPercentageOfCombinedPensionPlanObligations
Namespace Prefix:	cp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Expected Return On Fund Assets Calculated Using Market Related Assets Values Developed, Period

+ References

No definition available.

+ Details

Name:	cp_ExpectedReturnOnFundAssetsCalculatedUsingMarketRelatedAssetsValuesDevelopedPeriod
Namespace Prefix:	cp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum value of underlying asset represented by financial derivatives, excluding currency forwards.

+ References

No definition available.

+ Details

Name:	cp_MaximumValueOfUnderlyingAssetRepresentedByFinancialDerivativesExcludingCurrencyForwards
Namespace Prefix:	cp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Payments to employees, their beneficiaries or estates or to third-party benefit administrators.

+ References

No definition available.

+ Details

Name:	cp_PaymentsToEmployeesTheirBeneficiariesOrEstatesOrToThirdPartyBenefitAdministrators
Namespace Prefix:	cp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of combined plan obligations, other benefit plans.

+ References

No definition available.

+ Details

Name:	cp_PercentageOfCombinedPlanObligationsOtherBenefitPlans
Namespace Prefix:	cp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of defined benefit pension plan assets exposed to foreign currency risk.

+ References

No definition available.

+ Details

Name:	cp_PercentageOfDefinedBenefitPlanExposedToForeignCurrencyRisk
Namespace Prefix:	cp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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_DeferredCompensationArrangementWithIndividualPostretirementBenefitsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accumulated Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6503844

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

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

- Definition

The amount of employer securities or securities of parties related to the employer that are included in plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (n)
-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanAmountOfEmployerAndRelatedPartySecuritiesIncludedInPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Net increase or decrease in the plan benefit obligation during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanBenefitObligationPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

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

- Definition

Amount included in accumulated other comprehensive income (AOCI) related to gain (loss) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position.

+ References

No definition available.

+ Details

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

- Definition

Amount included in accumulated other comprehensive income (AOCI) related to prior service cost (credit) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position.

+ References

No definition available.

+ Details

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

- Definition

The date(s) used to measure (at least the majority of) plan assets and benefit obligations for defined benefit pension and other postretirement benefit plans. Disclosure required by FAS 132R paragraph 5k prior to being amended by FAS 158.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanMeasurementDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of employer shares or related party shares included in plan assets.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanNumberOfSharesOfEquitySecuritiesIssuedByEmployerAndRelatedPartiesIncludedInPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

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

- Definition

Amount of contributions made to multiemployer plans by the employer. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=35742057&loc=SL14450702-114947

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=35742057&loc=SL14450691-114947

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=35742057&loc=SL14450657-114947

+ Details

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

- Details

Name:	us-gaap_InvestmentTypeAxis=cp_NoteOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=cp_NoteThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_NotesPayableToBanksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cp_SixPointOneTwoFivePercentOneHundredYearNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cp_PercentageOfExposureToVariousCurrenciesAxis=cp_USCurrencyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cp_PercentageOfExposureToVariousCurrenciesAxis=cp_EuropeanCurrenciesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cp_PercentageOfExposureToVariousCurrenciesAxis=cp_OtherCurrenciesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionCostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=cp_DomesticRegisteredAndForeignQualifiedDefinedBenefitPensionPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPensionPlansPostretirementOrSupplementalPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Pensions and Other Benefits - Additional Information (Detail) - CAD CAD in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2015
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Canadian pension plan as a percentage of combined plan assets	99.00%
Canadian pension plan as a percentage of combined plan obligations	98.00%
Percentage of combined plan obligations	96.00%
Basis of calculating market related value of net periodic benefit cost	5 year average of market values for plans' public equity + plans' fixed income, real estate and infrastructure securities
Period of average market values for calculating net periodic benefit cost	5 years
Measurement date used to determine the plan assets and the accrued benefit obligation	December 31
Increase (decrease) in pension and post-retirement benefit obligation	CAD 225
Target long term rate of return, net of all fees and expenses	7.75%
Maximum value of underlying assets represented by financial derivatives, excluding currency forwards	30.00%
Company's common shares in fund assets, Shares	188,276	184,392
Company's common shares in fund assets, Market Value	CAD 33	CAD 41
Contribution by the company	90	88	CAD 105
Payments to employees, their beneficiaries or estates or to third-party benefit administrators	33	26	32
Net cost of defined contribution plan	9	8	7
Multi-employer plan contributions	4	4	5
6.25% Unsecured Notes Par Value [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Company's common shares in fund assets, Market Value	3	2
6.25% Unsecured Notes Market Value [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Company's common shares in fund assets, Market Value	CAD 3	2
Notes Payable to Banks [Member] \| 6.125% 100-year Notes [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Interest rate	6.25%			6.125%
US Dollar [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Plans exposure to foreign currency risk percentage	44.00%
European Currencies [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Plans exposure to foreign currency risk percentage	14.00%
Other Currencies [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Plans exposure to foreign currency risk percentage	5.00%
Pension Plans, Defined Benefit [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Gain related to legacy plans	CAD 11
Defined benefit pension plans' accumulated benefit obligation	10,893	10,975
Unamortized actuarial loss expected to be recognized in next fiscal year	191
Unamortized prior service cost expected to be recognized in next fiscal year	7
Contribution by the company	81	80
Other Postretirement Benefit Plans, Defined Benefit [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Unamortized actuarial loss expected to be recognized in next fiscal year	3
Unamortized prior service cost expected to be recognized in next fiscal year	1
Contribution by the company	33	26
Pension Costs [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Contribution by the company	9	8	7
Canadian Registered and U.S. Qualified Defined Benefit Pension Plans [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Contribution by the company	69	67	86
Other Pension Plans, Postretirement or Supplemental Plans, Defined Benefit [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Contribution by the company	CAD 12	CAD 13	CAD 12