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v3.25.3

Other Assets - Additional Information (Detail) | Oct. 31, 2025
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Bottom of range [member] |
Disclosure of Other Assets [line items] |
Significant influence percentage of voting rights | 20.00%
Top of range [member] |
Disclosure of Other Assets [line items] |
Significant influence percentage of voting rights | 50.00%

X
- Definition Disclosure of other assets [line items] + References No definition available. + Details
Name: | bmo_DisclosureOfOtherAssetsLineItems
Namespace Prefix: | bmo_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Significant influence percentage of voting rights. + References No definition available. + Details
Name: | bmo_SignificantInfluencePercentageOfVotingRights
Namespace Prefix: | bmo_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |