cm:Concept: us-gaap:EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount
| Share-based Payment Arrangement, Amount Capitalized |
| us-gaap:EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount |
| Amount of cost capitalized for award under share-based payment arrangement. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount |