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Commitments, Guarantees, Pledged Assets, Provisions and Contingent Liabilities - Summary of Pledged Assets collateral and Activities (Parenthetical) (Detail) - CAD ($) $ in Millions	Oct. 31, 2025	Oct. 31, 2024
Disclosure commitments guarantees pledged assets provisions and contingent liabilities [line items]
Assets pledged as collateral	$ 430,416	$ 371,350
Federal Home Loan Bank Loans [member]
Disclosure commitments guarantees pledged assets provisions and contingent liabilities [line items]
Assets pledged as collateral	16,734	21,235
Bank assets [member]
Disclosure commitments guarantees pledged assets provisions and contingent liabilities [line items]
Assets pledged as collateral	245,657	221,366
Bank assets [member] | Securities [member] | NHA mortgaged back securities [member]
Disclosure commitments guarantees pledged assets provisions and contingent liabilities [line items]
Assets pledged as collateral	$ 6,690	$ 5,492

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- Definition

Line items represent commitments guarantees pledged assets provisions and contingent liabilities.

+ References

No definition available.

+ Details

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Namespace Prefix:	bmo_
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Balance Type:	na
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- Definition

The amount of financial assets that the entity has pledged as collateral for liabilities or contingent liabilities, including amounts that have been reclassified in accordance with paragraph 3.2.23(a) of IFRS 9. [Refer: Classes of contingent liabilities [domain]; Financial assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2024-01-01
-Paragraph 14
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2024-en-r&anchor=para_14_a&doctype=Standard
-URIDate 2024-03-27

+ Details

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- Details

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- Details

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- Details

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