Segmented information - Major customers (Details) - CAD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Disclosure of major customers [line items]
Revenue	$ 2,091,661,000	$ 2,156,852,000
One customer of Cameco's uranium and fuel services segments [member]
Disclosure of major customers [line items]
Revenue	$ 204,594,000	$ 197,847,000
Percentage of entity's revenue	10.00%	9.00%
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 economic benefits during the accounting period in the form of inflows or enhancements of assets or decreases of liabilities that result in an increase in equity, other than those relating to contributions from equity participants.

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+ Details