cm:Concept: us-gaap:EmployeeStockOwnershipPlanESOPWeightedAveragePurchasePriceOfSharesPurchased
| Employee Stock Ownership Plan (ESOP), Weighted Average Purchase Price of Shares Purchased |
| us-gaap:EmployeeStockOwnershipPlanESOPWeightedAveragePurchasePriceOfSharesPurchased |
| Weighted average purchase price of capital shares purchased through an employee stock ownership plan. |
| cm:Concept |
| Share (num:perShareItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:EmployeeStockOwnershipPlanESOPWeightedAveragePurchasePriceOfSharesPurchased |