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Segmented information - Narrative (Details) - CAD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Operating Segments [Abstract]
Segment information	Cameco has two reportable segments: uranium and fuel services. Cameco's reportable segments are strategic business units with different products, processes and marketing strategies.
Care and maintenance	$ 153,924,000	$ 212,511,000
Severance costs	$ 260,000	$ 32,111,000

X

- Definition

Costs directly expense to cost of sales that are incurred to maintain production facilities during suspension of production.

+ References

No definition available.

+ Details

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- Definition

Compensation an employer provides to an employee who has been laid off, whose job has been eliminated, who has decided to leave the company through mutual agreement, or who has parted ways with the company for other reasons. Costs are directly expensed through cost of sales.

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No definition available.

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Period Type:	duration

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- References

No definition available.

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- Definition

The description of the factors used to identify the entity's reportable segments, including the basis of organisation (for example, whether management has chosen to organise the entity around differences in products and services, geographical areas, regulatory environments or a combination of factors and whether operating segments have been aggregated). [Refer: Geographical areas [member]; Operating segments [member]; Products and services [member]; Reportable segments [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2019-01-01
-Paragraph 22
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2019-en-r&anchor=para_22_a&doctype=Standard
-URIDate 2019-03-27

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