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Significant Events - Agreement to Construct and Own a Cogeneration Plant in Alberta (Details) $ in Millions | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2019 CAD ($) MW | Dec. 31, 2018 CAD ($) | Dec. 31, 2017 CAD ($) | Oct. 01, 2019 MW | Aug. 26, 2019 CAD ($) | Mar. 29, 2018 CAD ($)
Investment [Line Items] |  |  |  |  |  |
Gains on disposals of investments | $ 88 | $ 0 | $ 0 |  |  |
Plant In Alberta |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Capacity of facility (in megawatts) | MW |  |  |  | 40 |  |
EBITDA | 18 |  |  |  |  |
Plant In Alberta | Minimum |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Payments for development project expenditure | 105 |  |  |  |  |
Plant In Alberta | Maximum |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Payments for development project expenditure | $ 115 |  |  |  |  |
Power Purchase Arrangement |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Balancing pool compensation estimate, termination of contractual arrangement |  |  |  |  |  | $ 157
Termination of contractual arrangement, awarded amount |  |  |  |  | $ 56 |
SemCAMS | Plant In Alberta |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Equity participation percentage | 50.00% |  |  |  |  |
Genesee Unit 3 |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Capacity of facility (in megawatts) | MW | (466) |  |  |  |  |
Proportion of ownership interest in joint operation | 50.00% |  |  |  |  |
Cash transferred | $ 10 |  |  |  |  |
Payments from changes in ownership interests in subsidiaries that do not result in loss of control | 1 |  |  |  |  |
Consideration paid (received) | $ (77) |  |  |  |  |
Genesee Unit 3 | Capital Power |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Equity participation percentage | 10000.00% |  |  |  |  |
Keephills 3 |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Capacity of facility (in megawatts) | MW | 463 |  |  |  |  |
Equity participation percentage | 100.00% |  |  |  |  |
Proportion of ownership interest in joint operation | 50.00% |  |  |  |  |

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