Income Taxes - Rate Reconciliations (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Abstract]
Earnings (loss) before income taxes	$ (303)	$ 193	$ (96)
Net earnings (loss) attributable to non-controlling interests not subject to tax	2	(26)	(19)
Adjusted earnings (loss) before income taxes	$ (301)	$ 167	$ (115)
Statutory Canadian federal and provincial income tax rate	24.50%	26.50%	26.80%
Expected income tax expense (recovery)	$ (74)	$ 44	$ (31)
Increase (decrease) in income taxes resulting from:
Differences in effective foreign tax rates	3	5	(3)
Deferred income tax expense related to temporary difference on investment in subsidiaries	9	0	0
Writedown (reversal of writedown) of deferred income tax assets	8	(9)	27
Statutory and other rate differences	(7)	(31)	0
Other	11	8	1
Income tax expense (recovery)	$ (50)	$ 17	$ (6)
Effective tax rate	17.00%	10.00%	5.00%

The applicable income tax rate.

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The aggregate amount included in the determination of profit (loss) for the period in respect of current tax and deferred tax. [Refer: Current tax expense (income); Deferred tax expense (income)]

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The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that the entity does not separately disclose in the same statement or note. [Refer: Accounting profit; Applicable tax rate]

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The profit (loss) before tax expense or income. [Refer: Profit (loss)]

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The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to changes in the tax rate. [Refer: Accounting profit]

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The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to foreign tax rates. [Refer: Accounting profit]

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Income Taxes [Abstract]

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Profit (Loss) Before Tax, Adjusted For Non-Taxable Income, Non-controlling Interest

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Tax Effect Of Profit (Loss) Attributable To Non-Controlling Interest Not Subject To Tax

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