Income Taxes - Summary of Income Tax Expense (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Current income tax expense	$ 158	$ 39	$ 375	$ 427
Deferred income tax expense	38	130	151	190
Income tax expense	$ 196	$ 169	$ 526	$ 617