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Derivatives Instruments (Changes in Realized and Unrealized Gains (Losses) on Derivatives Receiving Regulatory Deferral) (Details) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items] |  |
Unrealized gain (loss) on derivatives receiving regulatory deferral | $ (228) | $ 666
FX forwards |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Realized (gain) loss on derivatives receiving regulatory deferral | (56) | 17
Regulatory deferral | Physical natural gas purchases |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total change derivative instruments on derivatives receiving regulatory deferral |  | (52)
Regulatory deferral | Physical natural gas purchases | Regulatory Assets |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Unrealized gain (loss) on derivatives receiving regulatory deferral |  | 0
Realized (gain) loss on derivatives receiving regulatory deferral |  | 0
Regulatory deferral | Physical natural gas purchases | Regulatory Liabilities |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Unrealized gain (loss) on derivatives receiving regulatory deferral |  | (3)
Realized (gain) loss on derivatives receiving regulatory deferral |  | 0
Regulatory deferral | Physical natural gas purchases | Inventory |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Realized (gain) loss on derivatives receiving regulatory deferral |  | 0
Regulatory deferral | Physical natural gas purchases | Regulated fuel for generation and purchased |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Realized (gain) loss on derivatives receiving regulatory deferral |  | (49)
Regulatory deferral | Physical natural gas purchases | Other |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Realized (gain) loss on derivatives receiving regulatory deferral |  | 0
Regulatory deferral | Commodity swaps and forwards |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total change derivative instruments on derivatives receiving regulatory deferral | 41 | (204)
Regulatory deferral | Commodity swaps and forwards | Regulatory Assets |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Unrealized gain (loss) on derivatives receiving regulatory deferral | (27) | (109)
Realized (gain) loss on derivatives receiving regulatory deferral | (8) | (5)
Regulatory deferral | Commodity swaps and forwards | Regulatory Liabilities |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Unrealized gain (loss) on derivatives receiving regulatory deferral | 11 | (73)
Realized (gain) loss on derivatives receiving regulatory deferral | 4 | 2
Regulatory deferral | Commodity swaps and forwards | Inventory |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Realized (gain) loss on derivatives receiving regulatory deferral | 11 | 4
Regulatory deferral | Commodity swaps and forwards | Regulated fuel for generation and purchased |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Realized (gain) loss on derivatives receiving regulatory deferral | 50 | (9)
Regulatory deferral | Commodity swaps and forwards | Other |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Realized (gain) loss on derivatives receiving regulatory deferral | 0 | (14)
Regulatory deferral | FX forwards |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Total change derivative instruments on derivatives receiving regulatory deferral | 24 | (17)
Regulatory deferral | FX forwards | Regulatory Assets |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Unrealized gain (loss) on derivatives receiving regulatory deferral | 5 | (3)
Realized (gain) loss on derivatives receiving regulatory deferral | 0 | 0
Regulatory deferral | FX forwards | Regulatory Liabilities |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Unrealized gain (loss) on derivatives receiving regulatory deferral | 33 | 0
Realized (gain) loss on derivatives receiving regulatory deferral | 0 | 0
Regulatory deferral | FX forwards | Inventory |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Realized (gain) loss on derivatives receiving regulatory deferral | (8) | (10)
Regulatory deferral | FX forwards | Regulated fuel for generation and purchased |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Realized (gain) loss on derivatives receiving regulatory deferral | (6) | (4)
Regulatory deferral | FX forwards | Other |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Realized (gain) loss on derivatives receiving regulatory deferral | $ 0 | $ 0

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4E -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4E + Details
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- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-28 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-07(7)(c)(3)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-07(7)(c)(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-07(7)(c)(6)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-07(7)(c)(7)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 5A -Subparagraph (SX 210.12-13A(Column F)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-5A + Details
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