Loans, Impaired Loans, and Allowance for Credit Losses - Disclosure - Loans, Impaired Loans, and Allowance for Credit Losses - Schedule of Incremental Lifetime ECL Impact (Detail) - CAD ($) $ in Millions	6 Months Ended	12 Months Ended
	Apr. 30, 2020	Oct. 31, 2019
Disclosure of detailed information about financial instruments [line items]
Difference - in amount	$ 259	$ 167
Difference - in percentage	3.80%	3.90%
Probability weighted method [member]
Disclosure of detailed information about financial instruments [line items]
Probability-weighted ECL	$ 6,769	$ 4,271
Base scenario [member]
Disclosure of detailed information about financial instruments [line items]
Base ECL	$ 6,510	$ 4,104