Basis of Presentation (Policies)	3 Months Ended
Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	These unaudited interim consolidated financial statements of Canadian Pacific Railway Limited (“CP”, or “the Company”), expressed in Canadian dollars, reflect management’s estimates and assumptions that are necessary for their fair presentation in conformity with generally accepted accounting principles in the United States of America (“GAAP”). They do not include all disclosures required under GAAP for annual financial statements and should be read in conjunction with the 2016 annual consolidated financial statements and notes included in CP's 2016 Annual Report on Form 10-K. The accounting policies used are consistent with the accounting policies used in preparing the 2016 annual consolidated financial statements, except for the newly adopted accounting policies discussed in Note 2. CP's operations can be affected by seasonal fluctuations such as changes in customer demand and weather-related issues. This seasonality could impact quarter-over-quarter comparisons. In management’s opinion, the unaudited interim consolidated financial statements include all adjustments (consisting of normal and recurring adjustments) necessary to present fairly such information. Interim results are not necessarily indicative of the results expected for the fiscal year.
Accounting Changes	Implemented in 2017 Compensation - Stock Compensation In March 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) 2016-09, Improvements to Employee Share-based Payment Accounting, under FASB Accounting Standards Codification ("ASC") Topic 718. The amendments clarify the guidance relating to treatment of excess tax benefits and deficiencies, acceptable forfeiture rate policies, and treatment of cash paid by an employer when directly withholding shares for tax-withholding purposes and the requirement to treat such cash flows as a financing activity. As a result of this ASU, excess tax benefits are no longer recorded in Additional paid-in capital and instead are applied against taxes payable or recognized in the interim consolidated statement of income. This ASU was effective for CP beginning on January 1, 2017. The Company has determined that there were no significant changes to disclosure or financial statement presentation and changes in accounting for excess tax benefits and deficiencies were not material as a result of adoption. Simplifying the Measurement of Inventory In July 2015, the FASB issued ASU 2015-11, Simplifying the Measurement of Inventory under FASB ASC Topic 330. The amendments require that reporting entities measure inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The amendments apply to inventory that is measured using the first-in, first-out or average cost basis. This ASU was effective for CP beginning on January 1, 2017 and was applied prospectively. The Company determined there were no changes to disclosure, financial statement presentation, or valuation of inventory as a result of adoption. Future changes Leases In February 2016, the FASB issued ASU 2016-02, Leases under FASB ASC Topic 842 which will supersede the lease recognition and measurement requirements in Topic 840 Leases. This new standard requires recognition of right-of-use assets and lease liabilities by lessees for those leases classified as finance and operating leases with a maximum term exceeding 12 months and will be effective for public entities for fiscal years, and interim periods within those years, beginning on or after December 15, 2018. For CP this will be effective commencing January 1, 2019. Entities are required to use a modified retrospective approach to adopt this new standard meaning there will be no impact to the consolidated statements of income, however, the comparative consolidated balance sheet will be adjusted to reflect the provisions of this standard. The Company has a detailed plan to implement the new standard and is assessing contractual arrangements, through a cross functional team, that may qualify as leases under the new standard. CP is also working with a vendor to implement a lease management system which will assist in delivering the required accounting changes. The impact of the new standard will be a material increase to right of use assets and lease liabilities on the consolidated balance sheet, primarily, as a result of operating leases currently not recognized on the balance sheet. The Company does not anticipate a material impact to the consolidated statement of income and is currently evaluating the impact adoption of this new standard will have on disclosure. Revenue from Contracts with Customers In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers under FASB ASC Topic 606. In March 2016, the FASB issued amendment ASU 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations as an update under FASB ASC Topic 606. The amendments clarify the principal versus agent guidance in determining whether to recognize revenue on a gross or net basis. The guidance in Topic 606, as amended, will be effective for public entities for fiscal years, and interim periods within those years, beginning on or after December 15, 2017. For CP this new standard will be effective commencing January 1, 2018, and CP has the option of adopting the new standard by either a full retrospective or a modified retrospective approach. CP has analyzed contracts for a significant proportion of the Company’s annual rail freight revenue, which represents greater than 95% of CP’s annual revenues, and has concluded that recognizing these revenues over time as rail freight services are performed continues to be appropriate. Further detailed reviews of a variety of specific contractual terms that could potentially represent additional performance obligations, reassessment of certain arrangements in the context of the new guidance on principal versus agent, and an assessment of required new disclosures is also currently being performed. CP is also continuing to assess whether to apply the full or modified retrospective adoption method on transition. At this time CP does not expect a material change to revenue recognition from adopting this standard. Intangibles - Goodwill and Other In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment under FASB ASC Topic 350. This is intended to simplify how an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. The amendments are effective for CP beginning on January 1, 2020. Entities are required to apply the amendments in this Update prospectively from the date of adoption. The Company does not anticipate that the adoption of this ASU will impact CP's financial statements as there is a sufficient excess between the fair value and carrying value of CP's goodwill. Furthermore CP expects to continue to apply the Step 0 qualitative assessment when testing for goodwill impairment. Compensation - Retirement Benefits In March 2017, the FASB issued ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost under FASB ASC Topic 715. The amendments clarify presentation requirements for net periodic pension cost and net periodic post-retirement benefit cost and require that an employer report the current service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net periodic benefit cost are required to be presented in the consolidated statement of income separately from the current service cost component and outside a subtotal of income from operations if one is presented. The amendments also restrict capitalization to the current service cost component when applicable. The amendments are effective for CP beginning on January 1, 2018. The amendments related to presentation are required to be applied retrospectively and the restrictions on capitalization of the current service cost component are applicable prospectively on the date of adoption. Adoption of this ASU will result in a $67 million and $43 million decrease in operating income for the three months ended March 31, 2017 and 2016, respectively, and an estimated corresponding full year decrease of $272 million and $167 million for the years ended December 31, 2017 and 2016, respectively. There will be no change to net income or earnings per share as a result of adoption of this new standard. The new guidance restricting capitalization of pensions to the current service cost component of net periodic benefit cost will have no impact to operating income or amounts capitalized because the Company currently only capitalizes an appropriate portion of current service cost for self-constructed properties. CP is currently assessing the disclosure requirements of this ASU.

Implemented in 2017

Compensation - Stock Compensation

In March 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) 2016-09, Improvements to Employee Share-based Payment Accounting, under FASB Accounting Standards Codification ("ASC") Topic 718. The amendments clarify the guidance relating to treatment of excess tax benefits and deficiencies, acceptable forfeiture rate policies, and treatment of cash paid by an employer when directly withholding shares for tax-withholding purposes and the requirement to treat such cash flows as a financing activity. As a result of this ASU, excess tax benefits are no longer recorded in Additional paid-in capital and instead are applied against taxes payable or recognized in the interim consolidated statement of income. This ASU was effective for CP beginning on January 1, 2017. The Company has determined that there were no significant changes to disclosure or financial statement presentation and changes in accounting for excess tax benefits and deficiencies were not material as a result of adoption.

Simplifying the Measurement of Inventory

In July 2015, the FASB issued ASU 2015-11, Simplifying the Measurement of Inventory under FASB ASC Topic 330. The amendments require that reporting entities measure inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The amendments apply to inventory that is measured using the first-in, first-out or average cost basis. This ASU was effective for CP beginning on January 1, 2017 and was applied prospectively. The Company determined there were no changes to disclosure, financial statement presentation, or valuation of inventory as a result of adoption.

Future changes

Leases

In February 2016, the FASB issued ASU 2016-02, Leases under FASB ASC Topic 842 which will supersede the lease recognition and measurement requirements in Topic 840 Leases. This new standard requires recognition of right-of-use assets and lease liabilities by lessees for those leases classified as finance and operating leases with a maximum term exceeding 12 months and will be effective for public entities for fiscal years, and interim periods within those years, beginning on or after December 15, 2018. For CP this will be effective commencing January 1, 2019. Entities are required to use a modified retrospective approach to adopt this new standard meaning there will be no impact to the consolidated statements of income, however, the comparative consolidated balance sheet will be adjusted to reflect the provisions of this standard. The Company has a detailed plan to implement the new standard and is assessing contractual arrangements, through a cross functional team, that may qualify as leases under the new standard. CP is also working with a vendor to implement a lease management system which will assist in delivering the required accounting changes. The impact of the new standard will be a material increase to right of use assets and lease liabilities on the consolidated balance sheet, primarily, as a result of operating leases currently not recognized on the balance sheet. The Company does not anticipate a material impact to the consolidated statement of income and is currently evaluating the impact adoption of this new standard will have on disclosure.

Revenue from Contracts with Customers

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers under FASB ASC Topic 606. In March 2016, the FASB issued amendment ASU 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations as an update under FASB ASC Topic 606. The amendments clarify the principal versus agent guidance in determining whether to recognize revenue on a gross or net basis. The guidance in Topic 606, as amended, will be effective for public entities for fiscal years, and interim periods within those years, beginning on or after December 15, 2017. For CP this new standard will be effective commencing January 1, 2018, and CP has the option of adopting the new standard by either a full retrospective or a modified retrospective approach. CP has analyzed contracts for a significant proportion of the Company’s annual rail freight revenue, which represents greater than 95% of CP’s annual revenues, and has concluded that recognizing these revenues over time as rail freight services are performed continues to be appropriate. Further detailed reviews of a variety of specific contractual terms that could potentially represent additional performance obligations, reassessment of certain arrangements in the context of the new guidance on principal versus agent, and an assessment of required new disclosures is also currently being performed. CP is also continuing to assess whether to apply the full or modified retrospective adoption method on transition. At this time CP does not expect a material change to revenue recognition from adopting this standard.

Intangibles - Goodwill and Other

In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment under FASB ASC Topic 350. This is intended to simplify how an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. The amendments are effective for CP beginning on January 1, 2020. Entities are required to apply the amendments in this Update prospectively from the date of adoption. The Company does not anticipate that the adoption of this ASU will impact CP's financial statements as there is a sufficient excess between the fair value and carrying value of CP's goodwill. Furthermore CP expects to continue to apply the Step 0 qualitative assessment when testing for goodwill impairment.

Compensation - Retirement Benefits

In March 2017, the FASB issued ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost under FASB ASC Topic 715. The amendments clarify presentation requirements for net periodic pension cost and net periodic post-retirement benefit cost and require that an employer report the current service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net periodic benefit cost are required to be presented in the consolidated statement of income separately from the current service cost component and outside a subtotal of income from operations if one is presented. The amendments also restrict capitalization to the current service cost component when applicable. The amendments are effective for CP beginning on January 1, 2018. The amendments related to presentation are required to be applied retrospectively and the restrictions on capitalization of the current service cost component are applicable prospectively on the date of adoption. Adoption of this ASU will result in a $67 million and $43 million decrease in operating income for the three months ended March 31, 2017 and 2016, respectively, and an estimated corresponding full year decrease of $272 million and $167 million for the years ended December 31, 2017 and 2016, respectively. There will be no change to net income or earnings per share as a result of adoption of this new standard. The new guidance restricting capitalization of pensions to the current service cost component of net periodic benefit cost will have no impact to operating income or amounts capitalized because the Company currently only capitalizes an appropriate portion of current service cost for self-constructed properties. CP is currently assessing the disclosure requirements of this ASU.