cm:Concept: us-gaap:ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months
| Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months |
| us-gaap:ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months |
| The estimated net amount of unrealized gains or losses on foreign currency cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months |