cm:Table: us-gaap:SecuritiesPurchasedUnderAgreementsToResellAllowanceForCreditLossTable
| Securities Purchased under Agreements to Resell, Allowance for Credit Loss [Table] |
| us-gaap:SecuritiesPurchasedUnderAgreementsToResellAllowanceForCreditLossTable |
| Disclosure of information about allowance for credit loss on securities purchased under agreement to resell. |
| cm:Table |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:SecuritiesPurchasedUnderAgreementsToResellAllowanceForCreditLossTable |