cm:Concept: us-gaap:RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths
| Repayments of Short-term Debt, Maturing in More than Three Months |
| us-gaap:RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths |
| The cash outflow from a repayment of a borrowing having initial term of repayment of more than three months but less than one year or one operating cycle (if the normal cycle is more than one year). |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths |