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Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions, $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 CAD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 CAD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 CAD ($)
Asset Impairment Charges |  |  |  |  |
Impairment charges | $ 25 |  | $ 34 |  |
Asset Impairment Charges, net of tax | 26 |  |  |  |
Goodwill |  |  |  |  |
Goodwill | 5,720 |  | 5,835 |  | $ 6,313
Goodwill impairment charge | 0 |  | 30 |  |
TECO Energy |  |  |  |  |
Goodwill |  |  |  |  |
Goodwill | 5,649 |  |  |  |
GBPC |  |  |  |  |
Asset Impairment Charges |  |  |  |  |
Asset Impairment Charges, net of tax |  |  |  | $ 18 |
Proceeds from Insurance Settlement, Operating Activities |  | $ 18 |  |  |
Goodwill |  |  |  |  |
Goodwill | $ 68 |  | 70 |  |
Goodwill impairment charge |  |  | $ 30 |  |
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount | 5.00% |  |  |  |

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