cm:Concept: us-gaap:ProceedsFromIssuanceOfSubordinatedLongTermDebt
| Proceeds from Issuance of Subordinated Long-term Debt |
| us-gaap:ProceedsFromIssuanceOfSubordinatedLongTermDebt |
| The cash inflow from a borrowing where a lender is placed in a lien position behind debt having a higher priority of repayment (senior) in liquidation of the entity's assets or underlying collateral. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:ProceedsFromIssuanceOfSubordinatedLongTermDebt |