cm:Concept: us-gaap:SharesHeldInEmployeeStockOptionPlanAllocated
| Shares Held in Employee Stock Option Plan, Allocated |
| us-gaap:SharesHeldInEmployeeStockOptionPlanAllocated |
| Number of allocated shares held by the Employee Stock Option Plan at balance sheet date. Allocated shares are shares that have been assigned to individual participant accounts based on a known formula. |
| cm:Concept |
| Shares (xbrli:sharesItemType) |
| As Of (instant) |
| (no balance type) |
| false |
| us-gaap:SharesHeldInEmployeeStockOptionPlanAllocated |