Segmented information - Major customers (Details) - CAD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Disclosure of major customers [line items]
Revenue	$ 1,800,073,000	$ 1,862,925,000
Major customer(s) of Cameco's uranium and fuel services segments [member]
Disclosure of major customers [line items]
Revenue	$ 457,560,000	$ 422,740,000
Percentage of entity's revenue	25.00%	24.00%
Information about major customers	As customers are relatively few in number, accounts receivable from any individual customer may periodically exceed 10% of accounts receivable depending on delivery schedule.

The income arising in the course of an entity's ordinary activities. Income is increases in assets, or decreases in liabilities, that result in increases in equity, other than those relating to contributions from holders of equity claims.

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+ Details