cm:Concept: us-gaap:PreferredStockReasonWhySecurityIsNotRedeemable
| Preferred Stock, Reason why Security is Not Redeemable |
| us-gaap:PreferredStockReasonWhySecurityIsNotRedeemable |
| If the security is not redeemable currently (for example, because a contingency has not been met), and it is not probable that the security will become redeemable, provide the reason why it is not probable that the security will become redeemable. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:PreferredStockReasonWhySecurityIsNotRedeemable |