Basis of Presentation	12 Months Ended
Dec. 31, 2025
Accounting Policies [Abstract]
Basis of Presentation	2. Basis of presentation: The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Xenon Pharmaceuticals USA Inc., which was incorporated in Delaware on December 2, 2016. All intercompany transactions and balances have been eliminated in consolidation. The consolidated financial statements are presented in U.S. dollars and have been prepared in accordance with generally accepted accounting principles in the United States ("GAAP"). Certain information has been reclassified to conform with the financial presentation adopted for the current year.

The entire disclosure for the basis of accounting, or basis of presentation, used to prepare the financial statements (for example, US Generally Accepted Accounting Principles, Other Comprehensive Basis of Accounting, IFRS).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 235
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/235/tableOfContent

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