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Derivatives Instruments (Credit Risk) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 CAD ($) NumberOfDays	Dec. 31, 2018 CAD ($)
Credit Derivatives [Line Items]
Concentration Risk, maximum exposure	$ 1,119	$ 1,382
Total cash deposits/collateral on hand	101	103
Receivables, net
Credit Derivatives [Line Items]
Concentration Risk, maximum exposure	1,032	1,215
Credit Concentration Risk
Credit Derivatives [Line Items]
Concentration Risk, maximum exposure	860	1,035
Total cash deposits/collateral on hand	259	346
Credit Concentration Risk | Receivables, net
Credit Derivatives [Line Items]
Financial assets, considered to be past due	115	118
Fair Value, Financial assets, considered to be past due	$ 106	$ 107
Average number of days financial asset outstanding | NumberOfDays	71

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The average number of days outstanding for financial assets, considered o be past due.

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Amount of accounts receivable past due, classified as noncurrent.

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-Publisher FASB
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Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity.

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Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

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This item represents disclosure of all significant concentrations of credit risk or market risk arising from the subject financial instrument (as defined), whether from an individual counterparty or groups of counterparties.

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