cm:Concept: us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost
| Share-based Payment Arrangement, Accelerated Cost |
| us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost |
| Amount of additional cost recognized for award under share-based payment arrangement from occurrence of event accelerating recognition of cost. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost |