cm:Concept: us-gaap:RetainedInvestmentDerecognizedAssetMeasurementInput
| Retained Investment, Derecognized Asset, Measurement Input |
| us-gaap:RetainedInvestmentDerecognizedAssetMeasurementInput |
| Value of input used to measure direct or indirect retained investment in derecognized group of assets constituting transfer of business or nonprofit activity, excluding conveyance of oil and gas mineral right and transfer of product or service in contract with customer. |
| cm:Concept |
| Decimal (xbrli:decimalItemType) |
| As Of (instant) |
| (no balance type) |
| false |
| us-gaap:RetainedInvestmentDerecognizedAssetMeasurementInput |