cm:Concept: us-gaap:EmployeeServiceShareBasedCompensationCashReceivedFromExerciseOfStockOptions
| Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options (Deprecated 2017-01-31) |
| us-gaap:EmployeeServiceShareBasedCompensationCashReceivedFromExerciseOfStockOptions |
| Aggregate proceeds received by the entity during the annual period from exercises of stock or unit options and conversion of similar instruments granted under equity-based payment arrangements. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:EmployeeServiceShareBasedCompensationCashReceivedFromExerciseOfStockOptions |