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Derivatives (Master Netting Agreements) (Details) - Designated as Hedging Instrument [Member] - CAD CAD in Millions | Dec. 31, 2016 | Dec. 31, 2015
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Derivative Asset, Fair Value, Amount Not Offset Against Collateral [Abstract] |  |
Derivative Asset, Collateral, Obligation to Return Cash, Offset | CAD 131 | CAD 240
Derivative Liability, Fair Value, Amount Not Offset Against Collateral [Abstract] |  |
Derivative Liability, Collateral, Right to Reclaim Cash, Offset | 131 | 240
Regulatory Deferral Hedge [Member] |  |
Derivative Asset, Fair Value, Amount Not Offset Against Collateral [Abstract] |  |
Derivative Asset, Collateral, Obligation to Return Cash, Offset | 10 | 0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral [Abstract] |  |
Derivative Liability, Collateral, Right to Reclaim Cash, Offset | 10 | 0
Held for Trading Hedge [Member] |  |
Derivative Asset, Fair Value, Amount Not Offset Against Collateral [Abstract] |  |
Derivative Asset, Collateral, Obligation to Return Cash, Offset | 121 | 240
Derivative Liability, Fair Value, Amount Not Offset Against Collateral [Abstract] |  |
Derivative Liability, Collateral, Right to Reclaim Cash, Offset | CAD 121 | CAD 240

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- Definition Amount of obligation to return cash collateral under master netting arrangements 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 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details
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- References No definition available. + Details
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- Definition Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 + Details
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- Details
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- Details
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