cm:Concept: us-gaap:LoansAndLeasesReceivableGainLossOnSalesNet
| Loans and Leases Receivable, Gain (Loss) on Sales, Net |
| us-gaap:LoansAndLeasesReceivableGainLossOnSalesNet |
| Reflects the net positive or negative amount derived from subtracting from net proceeds of sale and the carrying amounts, net of allocated reserves, of financial assets transferred to third parties in transactions that qualify for sales treatment. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:LoansAndLeasesReceivableGainLossOnSalesNet |