FV Measurements (Change in Fair Value of Level 3 Financial Assets) (Details) $ in Millions	12 Months Ended
Dec. 31, 2023 CAD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 90
Realized gains included in fuel for generation and purchased power	(49)
Unrealized gains included in regulatory liabilities	(3)
Total realized and unrealized gains (losses) included in non-regulated operating revenues	(4)
Ending Balance	34
Regulatory deferral \| Physical natural gas purchases \| Energy Related derivative
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	52
Realized gains included in fuel for generation and purchased power	(49)
Unrealized gains included in regulatory liabilities	(3)
Total realized and unrealized gains (losses) included in non-regulated operating revenues	0
Ending Balance	0
Not Designated as Hedging Instrument \| Energy Related derivative \| Non-regulated operating revenues
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	90
Realized gains included in fuel for generation and purchased power	(49)
HFT derivatives \| Energy Related derivative \| Non-regulated operating revenues
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	90
Realized gains included in fuel for generation and purchased power	(49)
Unrealized gains included in regulatory liabilities	(3)
Total realized and unrealized gains (losses) included in non-regulated operating revenues	(4)
Ending Balance	34
HFT derivatives \| Power \| Energy Related derivative
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	4
Realized gains included in fuel for generation and purchased power	0
Unrealized gains included in regulatory liabilities	0
Total realized and unrealized gains (losses) included in non-regulated operating revenues	(4)
Ending Balance	0
HFT derivatives \| Natural gas \| Energy Related derivative
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	34
Realized gains included in fuel for generation and purchased power	0
Unrealized gains included in regulatory liabilities	0
Total realized and unrealized gains (losses) included in non-regulated operating revenues	0
Ending Balance	$ 34

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Amount of increase (decrease) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-SubTopic 10
-Topic 820
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Amount of gain (loss) recognized in income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
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-Section 50
-Paragraph 2
-Subparagraph (c)(1)
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-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-3

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- Definition

Amount of gain (loss) recognized in other comprehensive income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1a)
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