Risk Management Activities - Additional Information (Details) - CAD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure of nature and extent of risks arising from financial instruments [line items]
Collateral paid (Note 15)	$ 42	$ 105
Financial assets pledged as collateral for liabilities or contingent liabilities	3	17
Derivative, contingent feature, additional collateral requirement	51	120
Asset-backed debt instruments held	920
Debt instruments held	1,217
Commodity Price Risk - Proprietary Trading [Member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Value at risk	1	2	$ 5
Commodity Price Risk - Generation [Member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Value at risk	25	18	16
Commodity Price Risk - Generation - Mark To Market Value [Member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Value at risk	8	13	$ 5
Letter of credit
Disclosure of nature and extent of risks arising from financial instruments [line items]
Collateral posted on derivative liabilities	$ 112	$ 120

The amount of debt instruments held that are backed by underlying assets. [Refer: Debt instruments held]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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The amount of current non-cash collateral assets (such as debt or equity instruments) provided to a transferee, for which the transferee has the right by contract or custom to sell or repledge the collateral.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The amount of instruments representing indebtedness held by the entity.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
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-IssueDate 2018-01-01
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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

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No definition available.

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The amount of financial assets that the entity has pledged as collateral for liabilities or contingent liabilities, including amounts that have been reclassified in accordance with paragraph 3.2.23(a) of IFRS 9. [Refer: Contingent liabilities [member]; Financial assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The measure of a potential loss exposure as a result of future market movements, based on a specified confidence interval and measurement horizon.

+ References

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Collateral on Derivative Instruments

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