cm:Concept: us-gaap:CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths
| Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months |
| us-gaap:CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths |
| The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths |