cm:Concept: us-gaap:DeferredCompensationShareBasedArrangementsLiabilityCurrent
| Deferred Compensation Share-based Arrangements, Liability, Current |
| us-gaap:DeferredCompensationShareBasedArrangementsLiabilityCurrent |
| Aggregate carrying value as of the balance sheet date of the liabilities for stock option plans and other equity-based compensation arrangements payable within one year (or the operating cycle, if longer). |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:DeferredCompensationShareBasedArrangementsLiabilityCurrent |