Loans - Summary of Credit Quality of Net Business and Government Loans and Acceptances (Parenthetical) (Detail) $ in Millions	Oct. 31, 2017 CAD ($)
Disclosure of internal credit grades [abstract]
Customers' liability under acceptances	$ 8,824

Business and government customer liabilities under acceptances.

No definition available.

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