cm:Concept: us-gaap:ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue
| Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value |
| us-gaap:ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue |
| Fair value as of the balance sheet date of all foreign currency derivative assets not designated as hedging instruments. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue |