cm:Concept: us-gaap:FairValueMeasurementsNonrecurringMeasurementPeriod
| Fair Value Measurements, Nonrecurring, Measurement Period |
| us-gaap:FairValueMeasurementsNonrecurringMeasurementPeriod |
| Description of period in which nonrecurring fair value measurement is taken. For example, but not limited to, the month or quarter in which the measurement is taken. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:FairValueMeasurementsNonrecurringMeasurementPeriod |