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Commitments and Contingencies (Principal Risks and Uncertainties) (Details) CAD in Millions, $ in Billions | Jul. 01, 2016 CAD | Jul. 01, 2016 USD ($) | Dec. 31, 2016 CAD | Dec. 31, 2015 CAD
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Loss Contingencies [Line Items] |  |  |  |
Public Utilities, Property, Plant and Equipment, Net |  |  | CAD 15,886 | CAD 6,258
Total Debt |  |  | CAD 15,000 |
TECO Energy Inc [Member] |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Business Combination, Consideration Transferred | CAD 13,900 | $ 10.7 |  |

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