Fair Value Measurement - Valuation Techniques and Quantitative Information About Significant Non-observable Inputs Used In Level 3 Financial Instruments (Detail) - Level 3 of fair value hierarchy [member] $ in Millions	Oct. 31, 2020 CAD ($)	Oct. 31, 2019 CAD ($)	Oct. 31, 2018 CAD ($)
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial assets, fair value	$ 1,400	$ 1,737	$ 1,340
Financial liabilities, fair value	(294)	(869)	(782)
Deposits and other liabilities [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial liabilities, fair value	4	(601)	(423)
Corporate equity [member] | Securities mandatorily measured at FVTPL [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial assets, fair value	16	7	6
Corporate equity [member] | Equity securities designated at FVOCI [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial assets, fair value	240	291	285
Corporate debt [member] | Securities mandatorily measured at FVTPL [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial assets, fair value	25	23	26
Mortgage and asset backed [member] | Securities mandatorily measured at FVTPL [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial assets, fair value	135	173	319
Business and government [member] | Loans mandatorily measured at FVTPL [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial assets, fair value	626	831	482
Credit derivatives [member] | Derivative liabilities [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial liabilities, fair value	(107)	(112)	(131)
Credit derivatives [member] | Derivative Assets [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial assets, fair value	98	104	115
Equity derivatives [member] | Derivative liabilities [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial liabilities, fair value	(163)	(155)	(119)
Equity derivatives [member] | Derivative Assets [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial assets, fair value	212	252	107
Interest rate derivatives [member] | Derivative liabilities [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial liabilities, fair value	(28)	(1)	$ (109)
Interest rate derivatives [member] | Derivative Assets [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial assets, fair value	48	$ 56
Corporate equity limited partnership private companies [member] | Equity securities designated at FVOCI [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Financial assets, fair value	$ 240
Bottom of range [member] | Deposits and other liabilities [member] | Option pricing model [member] | Market volatility [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, liabilities	0.100
Bottom of range [member] | Deposits and other liabilities [member] | Option pricing model [member] | Market correlation [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, liabilities	(0.600)
Bottom of range [member] | Corporate equity [member] | Securities mandatorily measured at FVTPL [member] | Multi-period excess earnings method [member] | Earnings multiple [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	15.1
Bottom of range [member] | Corporate debt [member] | Securities mandatorily measured at FVTPL [member] | Discounted cash flow [member] | Discount rate [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.075
Bottom of range [member] | Mortgage and asset backed [member] | Securities mandatorily measured at FVTPL [member] | Discounted cash flow [member] | Credit spread [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.014
Bottom of range [member] | Mortgage and asset backed [member] | Securities mandatorily measured at FVTPL [member] | Market approach [member] | Market proxy or direct broker quote [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.5
Bottom of range [member] | Business and government [member] | Loans mandatorily measured at FVTPL [member] | Discounted cash flow [member] | Credit spread [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.006
Bottom of range [member] | Credit derivatives [member] | Derivative liabilities [member] | Market approach [member] | Market proxy or direct broker quote [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, liabilities	0
Bottom of range [member] | Credit derivatives [member] | Derivative Assets [member] | Market approach [member] | Market proxy or direct broker quote [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0
Bottom of range [member] | Equity derivatives [member] | Derivative liabilities [member] | Option pricing model [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, liabilities	0.130
Bottom of range [member] | Equity derivatives [member] | Derivative Assets [member] | Option pricing model [member] | Market correlation [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.350
Bottom of range [member] | Interest rate derivatives [member] | Derivative liabilities [member] | Option pricing model [member] | Market volatility [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, liabilities	0.171
Bottom of range [member] | Interest rate derivatives [member] | Derivative Assets [member] | Option pricing model [member] | Market volatility [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.171
Top of range [member] | Deposits and other liabilities [member] | Option pricing model [member] | Market volatility [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, liabilities	0.870
Top of range [member] | Deposits and other liabilities [member] | Option pricing model [member] | Market correlation [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, liabilities	1
Top of range [member] | Corporate equity [member] | Securities mandatorily measured at FVTPL [member] | Multi-period excess earnings method [member] | Earnings multiple [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	15.1
Top of range [member] | Corporate debt [member] | Securities mandatorily measured at FVTPL [member] | Discounted cash flow [member] | Discount rate [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.075
Top of range [member] | Mortgage and asset backed [member] | Securities mandatorily measured at FVTPL [member] | Discounted cash flow [member] | Credit spread [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.020
Top of range [member] | Mortgage and asset backed [member] | Securities mandatorily measured at FVTPL [member] | Market approach [member] | Market proxy or direct broker quote [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.5
Top of range [member] | Business and government [member] | Loans mandatorily measured at FVTPL [member] | Discounted cash flow [member] | Credit spread [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.021
Top of range [member] | Credit derivatives [member] | Derivative liabilities [member] | Market approach [member] | Market proxy or direct broker quote [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, liabilities	0.205
Top of range [member] | Credit derivatives [member] | Derivative Assets [member] | Market approach [member] | Market proxy or direct broker quote [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.205
Top of range [member] | Equity derivatives [member] | Derivative liabilities [member] | Option pricing model [member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, liabilities	0.980
Top of range [member] | Equity derivatives [member] | Derivative Assets [member] | Option pricing model [member] | Market correlation [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.960
Top of range [member] | Interest rate derivatives [member] | Derivative liabilities [member] | Option pricing model [member] | Market volatility [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, liabilities	0.973
Top of range [member] | Interest rate derivatives [member] | Derivative Assets [member] | Option pricing model [member] | Market volatility [Member]
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]
Significant unobservable input, assets	0.973