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Derivatives Instruments (Credit Risk) (Narrative) (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2020 CAD ($) Days | Dec. 31, 2019 CAD ($)
Credit Derivatives [Line Items] |  |
Concentration Risk, maximum exposure | $ 1,056 | $ 1,119
Total cash deposits/collateral on hand | 69 | 101
Receivables, net |  |
Credit Derivatives [Line Items] |  |
Concentration Risk, maximum exposure | 958 | 1,032
Credit Concentration Risk |  |
Credit Derivatives [Line Items] |  |
Concentration Risk, maximum exposure | 805 | 860
Total cash deposits/collateral on hand | 251 | 259
Credit Concentration Risk | Receivables, net |  |
Credit Derivatives [Line Items] |  |
Financial assets, considered to be past due | 123 | 115
Fair Value, Financial assets, considered to be past due | $ 101 | $ 106
Average number of days financial asset outstanding | Days | 70 |

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