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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. |

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