XML 213 R170.htm IDEA: XBRL DOCUMENT v3.25.3

Employee Compensation - Pension and Other Employee Future Benefits - Summary of Duration of Defined Benefit Obligation (Detail) - yr	12 Months Ended
	Oct. 31, 2025	Oct. 31, 2024
Pension Plans [member] | Canada [member]
Disclosure of defined benefit plans [line items]
Duration of defined benefit obligation	13.1	13
Pension Plans [member] | United States [member]
Disclosure of defined benefit plans [line items]
Duration of defined benefit obligation	7.3	7.5
Other employee future benefit plans [member]
Disclosure of defined benefit plans [line items]
Duration of defined benefit obligation	11.4	11.7

X

- Definition

Duration of defined benefit obligation.

+ References

No definition available.

+ Details

Name:	bmo_DurationOfDefinedBenefitObligation
Namespace Prefix:	bmo_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfDefinedBenefitPlansLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	ifrs-full_DefinedBenefitPlansAxis=bmo_PensionPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_GeographicalAreasAxis=country_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_GeographicalAreasAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_DefinedBenefitPlansAxis=bmo_OtherEmployeeFutureBenefitPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: