cm:Concept: us-gaap:ServicingAssetAtAmortizedValueRiskCharacteristicsDescription
| Servicing Asset at Amortized Cost, Risk Characteristics Description |
| us-gaap:ServicingAssetAtAmortizedValueRiskCharacteristicsDescription |
| Description of the risk characteristics of the underlying financial assets for servicing assets that are subsequently measured using the amortization method. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ServicingAssetAtAmortizedValueRiskCharacteristicsDescription |