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Derivatives Instruments (Credit Risk) (Details) $ in Millions | 12 Months Ended
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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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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13537-108611 + Details
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