The amount of outstanding funds that the entity is obligated to repay.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 55
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_55&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_Borrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The interest rate on borrowings. [Refer: Borrowings]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 7
-IssueDate 2025-01-01
-Paragraph 7
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2025-en-r&anchor=para_7&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_BorrowingsInterestRate
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The maturity of borrowings. [Refer: Borrowings]

+ References

+ Details

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

- Definition

The current portion of non-current borrowings. [Refer: Borrowings]

+ References

+ Details

Name:	ifrs-full_CurrentPortionOfLongtermBorrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

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

- Definition

The amount of loans received.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 112
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_112_c&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_LoansReceived
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The non-current portion of non-current borrowings. [Refer: Borrowings]

+ References

+ Details

Name:	ifrs-full_LongtermBorrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of notes and debentures issued by the entity.

+ References

+ Details

Name:	ifrs-full_NotesAndDebenturesIssued
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	ifrs-full_MaturityAxis=ifrs-full_NotLaterThanOneYearMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_MaturityAxis=ifrs-full_LaterThanOneYearAndNotLaterThanTwoYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_MaturityAxis=ifrs-full_LaterThanTwoYearsAndNotLaterThanThreeYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_MaturityAxis=ifrs-full_LaterThanThreeYearsAndNotLaterThanFourYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_MaturityAxis=ifrs-full_LaterThanFourYearsAndNotLaterThanFiveYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_MaturityAxis=ifrs-full_LaterThanFiveYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=ccj_SeriesFMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=ccj_SeriesHMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=ccj_SeriesIMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=ccj_UsTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long term debt (Long-term debt) (Details) - CAD ($)	12 Months Ended
Long term debt (Long-term debt) (Details) - CAD ($)	Dec. 31, 2025	Dec. 31, 2024	May 24, 2024
Disclosure of detailed information about borrowings [line items]
Debt	$ 996,348,000	$ 1,281,290,000
Less current portion	0	(285,707,000)
Long-term debt	996,348,000	995,583,000
2026 [Member]
Disclosure of detailed information about borrowings [line items]
Unsecured debentures	0
2027 [Member]
Disclosure of detailed information about borrowings [line items]
Unsecured debentures	399,302,000
2028 [Member]
Disclosure of detailed information about borrowings [line items]
Unsecured debentures	0
2029 [Member]
Disclosure of detailed information about borrowings [line items]
Unsecured debentures	0
2030 [Member]
Disclosure of detailed information about borrowings [line items]
Unsecured debentures	0
Thereafter [Member]
Disclosure of detailed information about borrowings [line items]
Unsecured debentures	597,046,000
Series F [Member]
Disclosure of detailed information about borrowings [line items]
Unsecured debentures	$ 99,416,000	99,395,000
Stated interest rates on debentures	5.09%
Maturity date of borrowings	November 14, 2042
Series H [Member]
Disclosure of detailed information about borrowings [line items]
Unsecured debentures	$ 399,302,000	398,936,000
Stated interest rates on debentures	2.95%
Maturity date of borrowings	October 21, 2027
Series I [Member]
Disclosure of detailed information about borrowings [line items]
Unsecured debentures	$ 497,630,000	497,252,000	$ 500,000,000
Stated interest rates on debentures	4.94%		4.94%
Maturity date of borrowings	May 24, 2031
Term Loan [Member]
Disclosure of detailed information about borrowings [line items]
Term loan	$ 0	$ 285,707,000