RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Restricted Long-Term Investments (Details) - CAD ($) $ in Millions	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025
Long-Lived Assets Held-for-sale [Line Items]
Purchase of restricted long-term investments	$ 202	$ 892
Sale of restricted long-term investments	$ 103	$ 801

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

No definition available.

+ Details

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- Definition

The cash outflow to acquire investments (not to include restricted cash) that are pledged or subject to withdrawal restrictions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-13

+ Details

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- Definition

The cash inflow associated with the sale of investments that are pledged or subject to withdrawal restrictions during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-12

+ Details

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