Securities - Summary of Securities (Detail) - CAD ($) $ in Millions	Oct. 31, 2025	Oct. 31, 2024
Disclosure of detailed information about financial instruments [abstract]
Securities measured and designated at FVOCI	$ 88,905	$ 76,693
Securities measured at amortized cost	65,471	71,610
Securities mandatorily measured and designated at FVTPL	128,859	106,042
Total securities	$ 283,235	$ 254,345

Securities mandatorily measured and designated at fair value asset through profit and loss.

No definition available.

Name:	cm_SecuritiesMandatorilyMeasuredAndDesignatedAtFairValueAssetThroughProfitAndLoss
Namespace Prefix:	cm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant