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Goodwill (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 CAD ($) MWh | Dec. 31, 2017 CAD ($) MWh
Disclosure of detailed information about intangible assets [line items] |  |
Goodwill (Note 18) | $ 464 | $ 463
Hydro |  |
Disclosure of detailed information about intangible assets [line items] |  |
Goodwill (Note 18) | 259 | 259
Wind and Solar |  |
Disclosure of detailed information about intangible assets [line items] |  |
Goodwill (Note 18) | 175 | 174
Energy Marketing |  |
Disclosure of detailed information about intangible assets [line items] |  |
Goodwill (Note 18) | $ 30 | $ 30
Minimum |  |
Disclosure of detailed information about intangible assets [line items] |  |
Electricity prices | MWh | 5.83 | 22
Discount rate used to calculate goodwill impairment | 5.30% | 5.50%
Maximum |  |
Disclosure of detailed information about intangible assets [line items] |  |
Electricity prices | MWh | 179 | 218
Discount rate used to calculate goodwill impairment | 6.20% | 6.00%

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