cm:Table: us-gaap:TransferOfCertainFinancialAssetsAccountedForAsSecuredBorrowingsTable
| Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Table] |
| us-gaap:TransferOfCertainFinancialAssetsAccountedForAsSecuredBorrowingsTable |
| Disclosure of information about the nature and risks of short-term collateralized financing obtained through repurchase agreements, securities lending transactions and repurchase-to-maturity transactions, accounted for as secured borrowings. |
| cm:Table |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:TransferOfCertainFinancialAssetsAccountedForAsSecuredBorrowingsTable |