cm:Concept: us-gaap:SharesSubjectToMandatoryRedemptionSettlementTermsDescription
| Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Description |
| us-gaap:SharesSubjectToMandatoryRedemptionSettlementTermsDescription |
| Describe the nature and terms of the financial instrument, and the rights and obligations embodied in the instrument. Include settlement alternatives, if any, in the contract and identify the entity that controls the settlement alternatives. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:SharesSubjectToMandatoryRedemptionSettlementTermsDescription |