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Derivatives Instruments (Realized and Unrealized Gains (Losses) with Respect to Other derivatives) (Details) shares in Millions, $ in Millions, $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 CAD ($) | Dec. 31, 2019 CAD ($) | Dec. 31, 2020 USD ($) shares
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Equity derivative hedges, return of shares | shares |  |  | 2.8
Combined notional amount |  |  | $ 100
Foreign exchange forwards |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Total gains (losses) in net income | $ 13 | $ 0 |
Foreign exchange forwards | Operating, maintenance and general expense |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Unrealized gain on equity derivatives | 0 | 0 |
Total gains (losses) in net income | 0 | 0 |
Foreign exchange forwards | Other income (expense), net |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Unrealized gain on equity derivatives | 15 | 0 |
Total gains (losses) in net income | (2) | 0 |
Equity derivatives |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Total gains (losses) in net income | (4) | 28 |
Equity derivatives | Operating, maintenance and general expense |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Unrealized gain on equity derivatives | (1) | 1 |
Total gains (losses) in net income | (3) | 27 |
Equity derivatives | Other income (expense), net |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Unrealized gain on equity derivatives | 0 | 0 |
Total gains (losses) in net income | $ 0 | $ 0 |

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959 + Details
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