cm:Concept: us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardMethodOfMeasuringCostOfAward
| Share-based Compensation Arrangement by Share-based Payment Award, Method of Measuring Cost of Award |
| us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardMethodOfMeasuringCostOfAward |
| Description of method used for measuring cost of award under share-based payment arrangement. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardMethodOfMeasuringCostOfAward |