Earnings Per Share - Schedule of Basic and Diluted Per Share (Details) - CAD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Schedule of Basic and Diluted Per Share [Abstract]
Net income (loss) attributable to Telesat Corporation Shares	$ (35,269)	$ 17,901	$ (29,811)	$ 38,591
Effect of diluted securities		1,852		3,789
Diluted net income (loss) attributable to Telesat Corporation Shares	$ (35,269)	$ 19,753	$ (29,811)	$ 42,380

The profit (loss) attributable to ordinary equity holders of the parent entity, adjusted for the effects of all dilutive potential ordinary shares. [Refer: Profit (loss)]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 33
-IssueDate 2025-01-01
-Paragraph 70
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=33&code=ifrs-tx-2025-en-r&anchor=para_70_a&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_ProfitLossAttributableToOrdinaryEquityHoldersOfParentEntityIncludingDilutiveEffects
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration