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Percentage increase (decrease) in commodity prices.

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Proportion of outstanding debt with fixed rate.

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Quoted market yields.

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The adjustment to the basis (reference rate) used for calculation of the interest rate on borrowings. [Refer: Borrowings]

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The interest rate on borrowings. [Refer: Borrowings]

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The basis (reference rate) used for calculation of the interest rate on borrowings. [Refer: Borrowings]

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The amount of cash on hand and demand deposits, along with short-term, highly liquid investments that are readily convertible to known amounts of cash and that are subject to an insignificant risk of changes in value. [Refer: Cash; Cash equivalents]

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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

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The fair value of financial assets. [Refer: At fair value [member]; Financial assets]

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The amount of financial assets that the entity has pledged as collateral for liabilities or contingent liabilities, including amounts that have been reclassified in accordance with paragraph 3.2.23(a) of IFRS 9. [Refer: Contingent liabilities [member]; Financial assets]

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The gains (losses) resulting from change in the fair value of derivatives recognised in profit or loss. [Refer: Derivatives [member]]

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The nominal or face amount of a financial instrument, used to calculate payments made on that instrument.

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The amount of short-term deposits held by the entity that are not classified as cash equivalents. [Refer: Cash equivalents]

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Financial instruments - Narrative (Details)	12 Months Ended
Financial instruments - Narrative (Details)	Dec. 31, 2018 CAD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 CAD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 CAD ($)
Disclosure of detailed information about financial instruments [line items]
Gain (loss)	$ (81,081,000)		$ 56,250,000
Cash and cash equivalents	711,528,000		591,620,000		$ 320,278,000
Short-term investments	391,025,000		0
Amount of receivables sold	0		$ 120,470,000	$ 92,805,000
Pledged cash as security	$ 191,188,000
Quoted market yields	1.70%	1.70%
Bottom of range [member]
Disclosure of detailed information about financial instruments [line items]
Quoted market yields	1.90%	1.90%	1.60%	1.60%
Top of range [member]
Disclosure of detailed information about financial instruments [line items]
Quoted market yields	2.20%	2.20%	2.30%	2.30%
Interest rate swap contracts [member]
Disclosure of detailed information about financial instruments [line items]
Gain (loss)	$ 2,032,000		$ (4,014,000)
Credit risk [member]
Disclosure of detailed information about financial instruments [line items]
Cash and cash equivalents	711,528,000		591,620,000
Short-term investments	$ 391,025,000		$ 0
Interest rate risk [member]
Disclosure of detailed information about financial instruments [line items]
Proportion of outstanding debt that carries fixed rate	67.00%	67.00%	80.00%	80.00%
Interest rate risk [member] \| Interest rate swap contracts [member]
Disclosure of detailed information about financial instruments [line items]
Fair value of Cameco's interest rate swap assets	$ 856,000		$ (150,000)
Interest rate risk [member] \| Interest rate swap contracts [member] \| Series D senior unsecured debenture [member]
Disclosure of detailed information about financial instruments [line items]
Notional amount	$ 350,000,000
Interest rate risk [member] \| Interest rate swap contracts [member] \| Series D senior unsecured debenture [member] \| Floating interest rate [member]
Disclosure of detailed information about financial instruments [line items]
Interest rate basis	the three-month Canada Dealer Offered Rate	the three-month Canada Dealer Offered Rate
Margin rate	3.60%
Interest rate risk [member] \| Interest rate swap contracts [member] \| Series D senior unsecured debenture [member] \| Fixed interest rate [member]
Disclosure of detailed information about financial instruments [line items]
Interest rate	5.67%
Interest rate risk [member] \| Interest rate swap contracts [member] \| Series E senior unsecured debenture [Member]
Disclosure of detailed information about financial instruments [line items]
Notional amount	$ 150,000,000
Interest rate risk [member] \| Interest rate swap contracts [member] \| Series E senior unsecured debenture [Member] \| Floating interest rate [member]
Disclosure of detailed information about financial instruments [line items]
Interest rate basis	the three-month Canada Dealer Offered Rate	the three-month Canada Dealer Offered Rate
Margin rate	1.20%
Interest rate risk [member] \| Interest rate swap contracts [member] \| Series E senior unsecured debenture [Member] \| Fixed interest rate [member]
Disclosure of detailed information about financial instruments [line items]
Interest rate	3.75%
Commodity price risk [member]
Disclosure of detailed information about financial instruments [line items]
Percentage increase (decrease) in commodity price	30.00%	30.00%
Gain (loss)	$ (3,103,000)	$ (2,404,000)