cm:Concept: us-gaap:SharesSubjectToMandatoryRedemptionSettlementTermsReasonForUncertainRedemption
| Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Reason for Uncertain Redemption |
| us-gaap:SharesSubjectToMandatoryRedemptionSettlementTermsReasonForUncertainRedemption |
| If the financial instrument is not redeemable currently (for example, because a contingency has not been met), and it is not probable that the security will become redeemable, the reason for this uncertainty in redemption. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:SharesSubjectToMandatoryRedemptionSettlementTermsReasonForUncertainRedemption |