XML 222 R179.htm IDEA: XBRL DOCUMENT
v3.25.3

Commitments, Guarantees, Pledged Assets, Provisions and Contingent Liabilities - Summary of Maximum Amounts Payable Under Various Commitments (Parenthetical) (Detail) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Oct. 31, 2025 | Oct. 31, 2024
Disclosure commitments guarantees pledged assets provisions and contingent liabilities [line items] |  |
Fair value of derivative liabilities | $ 1 | $ 8
Other commitments | $ 1,664 | $ 4,511

X
- Definition Line items represent commitments guarantees pledged assets provisions and contingent liabilities. + References No definition available. + Details
Name: | bmo_DisclosureCommitmentsGuaranteesPledgedAssetsProvisionsAndContingentLiabilitiesLineItems
Namespace Prefix: | bmo_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The fair value of financial liabilities classified as credit default swaps. + References No definition available. + Details
Name: | bmo_FairValueOfFinancialLiabilitiesClassifiedAsCreditDefaultSwaps
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Other Commitment . + References No definition available. + Details
Name: | bmo_Othercommitment
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant