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Group entities (Details) | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
JV Inkai Associate [Member] |  |
Disclosure of subsidiaries [line items] |  |
Ownership interest in subsidiaries | 40.00% | 40.00%
Principal place of business of associate | Kazakhstan |
Cameco Fuel Manufacturing Inc. [member] |  |
Disclosure of subsidiaries [line items] |  |
Ownership interest in subsidiaries | 100.00% | 100.00%
Principal place of business of subsidiary | Canada |
Cameco Marketing Inc. [member] |  |
Disclosure of subsidiaries [line items] |  |
Ownership interest in subsidiaries | 100.00% | 100.00%
Principal place of business of subsidiary | Canada |
Cameco Inc. [member] |  |
Disclosure of subsidiaries [line items] |  |
Ownership interest in subsidiaries | 100.00% | 100.00%
Principal place of business of subsidiary | US |
Power Resources, Inc. [member] |  |
Disclosure of subsidiaries [line items] |  |
Ownership interest in subsidiaries | 100.00% | 100.00%
Principal place of business of subsidiary | US |
Crow Butte Resources, Inc. [member] |  |
Disclosure of subsidiaries [line items] |  |
Ownership interest in subsidiaries | 100.00% | 100.00%
Principal place of business of subsidiary | US |
NUKEM, Inc. [member] |  |
Disclosure of subsidiaries [line items] |  |
Ownership interest in subsidiaries | 100.00% | 100.00%
Principal place of business of subsidiary | US |
Cameco Australia Pty. Ltd. [member] |  |
Disclosure of subsidiaries [line items] |  |
Ownership interest in subsidiaries | 100.00% | 100.00%
Principal place of business of subsidiary | Australia |
Cameco Europe Ltd. [member] |  |
Disclosure of subsidiaries [line items] |  |
Ownership interest in subsidiaries | 100.00% | 100.00%
Principal place of business of subsidiary | Switzerland |

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