Description of business and basis of presentation (Policies)	6 Months Ended
Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	These unaudited interim consolidated financial statements ("Interim Consolidated Financial Statements") have been prepared in accordance with accounting principles generally accepted in the U.S. ("GAAP"). They do not include all of the information required for a complete set of annual financial statements prepared in accordance with GAAP and should be read in conjunction with the Company's audited consolidated financial statements as at and for the year ended December 31, 2025 ("last annual consolidated financial statements"). Selected explanatory notes are included to explain events and transactions that are significant to an understanding of the changes in the Company's financial position and results of operations since the last annual consolidated financial statements. These Interim Consolidated Financial Statements have been prepared using the same significant accounting policies used in the last annual consolidated financial statements, except for the adoption of new accounting standards (see Note 2). Amounts are stated in Canadian dollars unless otherwise noted. The Company's operations and income for interim periods can be affected by seasonal fluctuations such as changes in customer demand and weather conditions, and may not be indicative of annual results.
Recently adopted accounting standards & Accounting standards not yet adopted	Accounting Standards Update ("ASU") 2025-05 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets On January 1, 2026, the Company prospectively adopted ASU 2025-05, which simplifies estimating credit losses on current accounts receivable and current contract assets. Under the new guidance, CPKC elected to adopt a practical expedient allowing the Company to assume that conditions existing as of the balance sheet date will remain unchanged over the remaining life of the asset when developing reasonable and supportable forecasts for estimating expected credit losses. Adoption of ASU 2025-05 did not have a material impact on the Company's Interim Consolidated Financial Statements. Other accounting standards that became effective during the three and six months ended June 30, 2026, did not have a material impact on the Company's Interim Consolidated Financial Statements. Recently issued accounting pronouncements are not expected to have a material impact on the Company's financial position or results of operations upon adoption.

Description of business and basis of presentation (Policies)

6 Months Ended

Jun. 30, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

These unaudited interim consolidated financial statements ("Interim Consolidated Financial Statements") have been prepared in accordance with accounting principles generally accepted in the U.S. ("GAAP"). They do not include all of the information required for a complete set of annual financial statements prepared in accordance with GAAP and should be read in conjunction with the Company's audited consolidated financial statements as at and for the year ended December 31, 2025 ("last annual consolidated financial statements"). Selected explanatory notes are included to explain events and transactions that are significant to an understanding of the changes in the Company's financial position and results of operations since the last annual consolidated financial statements. These Interim Consolidated Financial Statements have been prepared using the same significant accounting policies used in the last annual consolidated financial statements, except for the adoption of new accounting standards (see Note 2). Amounts are stated in Canadian dollars unless otherwise noted.

The Company's operations and income for interim periods can be affected by seasonal fluctuations such as changes in customer demand and weather conditions, and may not be indicative of annual results.

Recently adopted accounting standards & Accounting standards not yet adopted

Accounting Standards Update ("ASU") 2025-05 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets

On January 1, 2026, the Company prospectively adopted ASU 2025-05, which simplifies estimating credit losses on current accounts receivable and current contract assets. Under the new guidance, CPKC elected to adopt a practical expedient allowing the Company to assume that conditions existing as of the balance sheet date will remain unchanged over the remaining life of the asset when developing reasonable and supportable forecasts for estimating expected credit losses. Adoption of ASU 2025-05 did not have a material impact on the Company's Interim Consolidated Financial Statements.

Other accounting standards that became effective during the three and six months ended June 30, 2026, did not have a material impact on the Company's Interim Consolidated Financial Statements. Recently issued accounting pronouncements are not expected to have a material impact on the Company's financial position or results of operations upon adoption.