cm:Concept: us-gaap:NetCreditLossOnLoansManagedOrSecuritizedOrAssetbackedFinancingArrangement
| Net Credit Loss on Loans Managed or Securitized or Asset-backed Financing Arrangement |
| us-gaap:NetCreditLossOnLoansManagedOrSecuritizedOrAssetbackedFinancingArrangement |
| Amount of credit loss after recoveries for transferred financial assets that continue to be recognized in the statement of financial position. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:NetCreditLossOnLoansManagedOrSecuritizedOrAssetbackedFinancingArrangement |