cm:Concept: us-gaap:InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue
| Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Liability at Fair Value |
| us-gaap:InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue |
| Fair value as of the balance sheet date of all derivative liabilities not designated as hedging instruments. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue |