cm:Concept: us-gaap:TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount
| Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount |
| us-gaap:TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount |
| Carrying amount of liabilities associated with financial assets accounted for as secured borrowings recognized in the transferor's statement of financial position at the end of each period presented. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount |