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Income Taxes (Composition of taxes on income from continuing operations) (Details) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] |  |  |
Deferred income taxes | $ 125 | $ 185 |
Income tax expense (recovery) | 61 | 69 |
Supplemental Tax Information [Abstract] |  |  |
Income before provision for income taxes | 771 | 816 |
Canada |  |  |
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] |  |  |
Current income taxes | (19) | 3 |
Deferred income taxes | 45 | 11 |
Operating loss carry forwards | (48) | (33) |
Supplemental Tax Information [Abstract] |  |  |
Income before provision for income taxes | 98 | 127 | $ 127
United States |  |  |
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] |  |  |
Current income taxes | (46) | (121) |
Deferred income taxes | 137 | 215 |
Investment tax credits | (9) | (4) |
Operating loss carry forwards | 0 | 0 |
Revaluation of US non-regulated deferred income taxes due to tax reform | 0 | 0 |
Supplemental Tax Information [Abstract] |  |  |
Income before provision for income taxes | 682 | 646 | 646
Other |  |  |
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] |  |  |
Current income taxes | 1 | 2 |
Deferred income taxes | 0 | (4) |
Operating loss carry forwards | 0 | 0 |
Supplemental Tax Information [Abstract] |  |  |
Income before provision for income taxes | $ (9) | $ 43 | $ 43

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- Definition Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 6.I.7) -URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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