Income Taxes - Summary of Reconciliation of Income Tax Expense (Detail) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Reconciliation of accounting profit multiplied by applicable tax rates [abstract]
Income before income taxes	$ 6,770	$ 6,220
Income tax expense at Canadian statutory tax rate	1,794	1,664
Increase (decrease) in income taxes due to:
Tax-exempt investment income	(171)	(260)
Differences in tax rate on income not subject to tax in Canada	(528)	(754)
Adjustments to taxes related to prior years	(96)	(106)
Tax rate change	27
Other differences	169	174
Income tax expense	$ 1,195	$ 718

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 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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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 revenues that are exempt from taxation. [Refer: Accounting profit]

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The product of the accounting profit multiplied by the applicable tax rate(s). [Refer: Accounting profit; Applicable tax rate]

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Income loss before tax.

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Increase decrease in income taxes.

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