Long-term receivables, investments and other (Long-term receivables, investments and other) (Details) $ in Thousands	12 Months Ended
Dec. 31, 2025 CAD ($) lb kg	Dec. 31, 2024 CAD ($) lb kg
Long-term receivables, investments and other [Abstract]
Derivatives	$ 21,166	$ 103
Investment tax credits	97,186	96,199
Amounts receivable related to tax dispute	209,125	209,125
Income tax receivable	65,653	0
Product loan	288,294	288,294
Other	4,959	3,268
Total (current and non current portion)	686,383	596,989
Less current portion	(39,138)	(1,093)
Net	$ 647,245	$ 595,896
Required percent to remit or secure of cash taxes and transfer pricing penalties, plus related interest and instalment penalties assessed	50.00%
Uranium Concentrate [Member] \| Orano Canada Inc [member]
Disclosure of products and services [line items]
Product loan quantity \| lb	5,400,000
Repayment on loan receivable \| lb	3,000,000	3,000,000
U3O8 [Member] \| Orano Canada Inc [member]
Disclosure of products and services [line items]
Product loan maturity	December 31, 2028
Product loan quantity \| lb	3,600,000	3,600,000
Undrawn Loan Receivables Quantity \| lb	1,200,000
Undrawn Loan Maturity Date	December 31, 2027
Uranium conversion supply [Member] \| Orano Canada Inc [member]
Disclosure of products and services [line items]
Product loan maturity	December 31, 2035
Product loan quantity \| kg	1,148,200	1,148,200
Maximum quantity of raw materials \| kg	1,148,200

Receivables from the tax authroities related to income tax disputes.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of current portion of long term receivables, investments and other items.

+ References

No definition available.

+ Details

Name:	ccj_CurrentRecivablesInvestmentsAndOther
Namespace Prefix:	ccj_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Investment tax credit receivable related to research and development.

+ References

No definition available.

+ Details

Name:	ccj_InvestementTaxCreditReceivableRelatedToResearchAndDevelopment
Namespace Prefix:	ccj_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The quantity of receivable from another party.

+ References

No definition available.

+ Details

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Namespace Prefix:	ccj_
Data Type:	dtr-2022:massItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of noncurrent receivables, investments and other.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Maximum quantity of raw materials

+ References

No definition available.

+ Details

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Namespace Prefix:	ccj_
Data Type:	dtr-2022:massItemType
Balance Type:	na
Period Type:	instant

- Definition

The maturity of loans and receivables.

+ References

No definition available.

+ Details

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Namespace Prefix:	ccj_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of receivables, investments and other items.

+ References

No definition available.

+ Details

Name:	ccj_ReceivablesInvestmentsAndOther
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Required Percent To Remit Or Secure Of Cash Taxes And Transfer Pricing Penalties, Plus Related Interest And Instalment Penalties Assessed

+ References

No definition available.

+ Details

Name:	ccj_RequiredPercentToRemitOrSecureOfCashTaxesAndTransferPricingPenaltiesPlusRelatedInterestAndInstalmentPenaltiesAssessed
Namespace Prefix:	ccj_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Returned Amount As Repayment To Loan Receivables Quantity

+ References

No definition available.

+ Details

Name:	ccj_ReturnedAmountAsRepaymentToLoanReceivablesQuantity
Namespace Prefix:	ccj_
Data Type:	dtr-2022:massItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Undrawn Loan Receivables Quantity

+ References

No definition available.

+ Details

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Namespace Prefix:	ccj_
Data Type:	dtr-2022:massItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	ifrs-full_CategoriesOfNoncurrentFinancialAssetsAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of financial assets classified as derivative instruments. [Refer: Financial assets; Derivatives [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
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-URIDate 2025-03-27

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount receivable by the entity that it does not separately disclose in the same statement or note.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
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-Subparagraph b
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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-URIDate 2025-03-27

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of receivables from taxes other than income tax. Income taxes include all domestic and foreign taxes that are based on taxable profits. Income taxes also include taxes, such as withholding taxes, that are payable by a subsidiary, associate or joint arrangement on distributions to the reporting entity.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
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-URIDate 2025-03-27

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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Balance Type:
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- Details

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- Details

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- Details

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