XML 172 R129.htm IDEA: XBRL DOCUMENT
v3.25.3

Insurance - Summary of the Insurance Liability by Remaining Coverage and Incurred Claims (Parenthetical) (Detail) - CAD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Oct. 31, 2025 | Oct. 31, 2024
Insurance service result [Line Items] |  |
Liabilities for incurred claims | $ 102 | $ 115
The Union Life [Member] |  |
Insurance service result [Line Items] |  |
Insurance contracts transferred | $ 798 |

X
- Definition Insurance contracts transferred. + References No definition available. + Details
Name: | bmo_InsuranceContractsTransferred
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | bmo_InsuranceServiceResultLineItems
Namespace Prefix: | bmo_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of the liabilities for incurred claims that arise from contracts within the scope of IFRS 17. [Refer: Liabilities for incurred claims [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 17 -IssueDate 2024-01-01 -Paragraph 130 -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=17&code=ifrs-tx-2024-en-r&anchor=para_130&doctype=Standard -URIDate 2024-03-27 + Details
Name: | ifrs-full_LiabilitiesForIncurredClaimsThatAriseFromContractsWithinScopeOfIFRS17
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | ifrs-full_InsuranceContractsAxis=bmo_TheUnionLifeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |