cm:Concept: us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesToBeRepurchasedNextYear
| Share-based Compensation Arrangement by Share-based Payment Award, Shares to be Repurchased Next Year |
| us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesToBeRepurchasedNextYear |
| An entity expecting to repurchase shares in the following period, generally discloses an estimate of the amount or range of shares to be repurchased. |
| cm:Concept |
| Shares (xbrli:sharesItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesToBeRepurchasedNextYear |