Securities - Additional Information (Detail) - CAD ($) $ in Millions	12 Months Ended
Oct. 31, 2025	Oct. 31, 2024
Disclosure of financial assets [line items]
Fair value of equity securities designated at FVOCI that were disposed	$ 0	$ 0
Net realized cumulative after-tax gains reclassifed from AOCI to retained earnings	2	(15)
Dividend income recognized on equity securities	3	3
Dividend income recognized on equity securities designated at FVOCI that were disposed	$ 0	$ 0

Fair value of investments in equity instruments measured at fair value through other comprehensive income disposed.

No definition available.

Name:	cm_FairValueOfInvestmentsInEquityInstrumentsMeasuredAtFairValueThroughOtherComprehensiveIncomeDisposed
Namespace Prefix:	cm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cumulative gain (loss) on disposal of investments in equity instruments that the entity has designated at fair value through other comprehensive income. [Refer: At fair value [member]; Other comprehensive income]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2024-01-01
-Paragraph 11B
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2024-en-r&anchor=para_11B_c&doctype=Standard
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_CumulativeGainLossOnDisposalOfInvestmentsInEquityInstrumentsDesignatedAsMeasuredAtFairValueThroughOtherComprehensiveIncome
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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_DisclosureOfFinancialAssetsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of dividends related to investments in equity instruments that the entity has designated at fair value through other comprehensive income, derecognised during the reporting period. [Refer: Investments in equity instruments designated at fair value through other comprehensive income [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2024-01-01
-Paragraph 11A
-Subparagraph d
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2024-en-r&anchor=para_11A_d&doctype=Standard
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_DividendsRecognisedForInvestmentsInEquityInstrumentsDesignatedAsMeasuredAtFairValueThroughOtherComprehensiveIncomeDerecognisedDuringPeriod
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of dividends related to investments in equity instruments that the entity has designated at fair value through other comprehensive income, held at the end of the reporting period. [Refer: Investments in equity instruments designated at fair value through other comprehensive income [member]]

+ References

+ Details

Name:	ifrs-full_DividendsRecognisedForInvestmentsInEquityInstrumentsDesignatedAsMeasuredAtFairValueThroughOtherComprehensiveIncomeHeldAtEndOfReportingPeriod
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration