cm:Concept: us-gaap:DescriptionOfForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsActivities
| Description of Foreign Currency Derivative Instruments Not Designated as Hedging Instruments Activities |
| us-gaap:DescriptionOfForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsActivities |
| General discussion of the entity's activities involving foreign currency derivatives not designated as hedging instruments. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DescriptionOfForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsActivities |