cm:Member: us-gaap:FairValueConcentrationOfRiskIdentifyingCharacteristicsMember
| Fair Value, Concentration of Risk, Identifying Characteristics [Member] |
| us-gaap:FairValueConcentrationOfRiskIdentifyingCharacteristicsMember |
| This element represents information about the (shared) activity, region, or economic characteristic that identifies the specific concentration of to the financial instrument (as defined). |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:FairValueConcentrationOfRiskIdentifyingCharacteristicsMember |