XML 176 R133.htm IDEA: XBRL DOCUMENT
v3.25.3

Insurance - Summary of Sensitivities of Earning to Increase or Decreases in Policy-related Assumptions (Detail) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Oct. 31, 2025 | Oct. 31, 2024
Gross carrying amount [member] | Actuarial assumption of mortality rates [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Mortality Rates (1% increase) CSM Gross | $ (8) | $ (17)
Mortality Rates (1% increase) Profit or Loss Gross | 1 | 1
Gross carrying amount [member] | Actuarial Assumption of Lapse Rates [Member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Lapse Rates (10% increase) CSM Gross | (45) | (151)
Lapse Rates (10% increase) Profit or Loss Gross | (82) | (10)
Gross carrying amount [member] | Actuarial Assumption of Expenses [Member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Expenses (5% increase) CSM Gross | (14) | (15)
Expenses (5% increase) Profit or Loss Gross | (1) |
Net amount [Member] | Actuarial assumption of mortality rates [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Mortality Rates (1% increase) CSM Net | 15 | 10
Mortality Rates (1% increase) Profit or Loss Net | 2 | 1
Net amount [Member] | Actuarial Assumption of Lapse Rates [Member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Lapse Rates (10% increase) CSM Net | 38 | (52)
Lapse Rates (10% increase) Profit or Loss Net | (74) | (4)
Net amount [Member] | Actuarial Assumption of Expenses [Member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Expenses (5% increase) CSM Net | (14) | $ (15)
Expenses (5% increase) Profit or Loss Net | $ (1) |

X
- Definition Five percent increase in expenses impact on gross csm. + References No definition available. + Details
Name: | bmo_FivePercentIncreaseInExpensesImpactOnGrossCsm
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Five percent increase in expenses impact on gross profit or loss. + References No definition available. + Details
Name: | bmo_FivePercentIncreaseInExpensesImpactOnGrossProfitOrLoss
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Five percent increase in expenses impact on net csm. + References No definition available. + Details
Name: | bmo_FivePercentIncreaseInExpensesImpactOnNetCSM
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Five percent increase in expenses impact on net profit or loss. + References No definition available. + Details
Name: | bmo_FivePercentIncreaseInExpensesImpactOnNetProfitOrLoss
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition One percent increase change in life mortality rates impact on gross profit or loss. + References No definition available. + Details
Name: | bmo_OnePercentIncreaseChangeInLifeMortalityRatesImpactOnGrossProfitOrLoss
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition One percent increase in life mortality rates impact on gross contractual service margin. + References No definition available. + Details
Name: | bmo_OnePercentIncreaseInLifeMortalityRatesImpactOnGrossContractualServiceMargin
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition One percent increase in life mortality rates impact on net contractual service margin. + References No definition available. + Details
Name: | bmo_OnePercentIncreaseInLifeMortalityRatesImpactOnNetContractualServiceMargin
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition One percent increase in life mortality rates impact on net profit or loss. + References No definition available. + Details
Name: | bmo_OnePercentIncreaseInLifeMortalityRatesImpactOnNetProfitOrLoss
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Ten percent increase in lapse rates impact on gross csm. + References No definition available. + Details
Name: | bmo_TenPercentIncreaseInLapseRatesImpactOnGrossCSM
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Ten percent increase in lapse rates impact on gross profit or loss. + References No definition available. + Details
Name: | bmo_TenPercentIncreaseInLapseRatesImpactOnGrossProfitOrLoss
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Ten percent increase in lapse rates impact on net csm. + References No definition available. + Details
Name: | bmo_TenPercentIncreaseInLapseRatesImpactOnNetCSM
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Ten percent increase in lapse rates impact on net profit or loss. + References No definition available. + Details
Name: | bmo_TenPercentIncreaseInLapseRatesImpactOnNetProfitOrLoss
Namespace Prefix: | bmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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_DisclosureOfSensitivityAnalysisForActuarialAssumptionsLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | bmo_ReconciliationAxis=ifrs-full_GrossCarryingAmountMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ActuarialAssumptionsAxis=ifrs-full_ActuarialAssumptionOfMortalityRatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ActuarialAssumptionsAxis=bmo_ActuarialAssumptionOfLapseRatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ActuarialAssumptionsAxis=bmo_ActuarialAssumptionOfExpensesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | bmo_ReconciliationAxis=bmo_NetAmountMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |