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Derivatives (Credit Risk Exposure) (Details) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Credit Derivatives [Line Items] |  |
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure | $ 1,394 | $ 1,290
Total cash deposits/collateral on hand | 119 | 91
Accounts Receivable [Member] |  |
Credit Derivatives [Line Items] |  |
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure | 1,148 | 1,019
Total cash deposits/collateral on hand | 247 | 271
Financial assets, considered to be past due | $ 90 | 104
Derivative, Credit Risk, Past Due Days Outstanding | 69 days |
Fair Value of assets | $ 78 | $ 91

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- Definition Amount of finacial assets that are past due related to Derivatives. + References No definition available. + Details
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- Definition Net amount after allowance for doubtful accounts of finacial assets that are past due related to Derivatives. + References No definition available. + Details
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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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611 + Details
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- Definition Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41678-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226016-175313 + Details
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