cm:Concept: us-gaap:DerivativeCreditRiskRelatedContingentFeaturesExistenceAndNature
| Derivative, Credit Risk Related Contingent Features, Existence and Nature |
| us-gaap:DerivativeCreditRiskRelatedContingentFeaturesExistenceAndNature |
| Description of the existence and nature of credit-risk-related contingent features related to derivative instruments (and nonderivative instruments that are designated and qualify as hedging instruments) that are in a net liability position at the end of the reporting period. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DerivativeCreditRiskRelatedContingentFeaturesExistenceAndNature |