cm:Axis: us-gaap:QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTransferredFinancialAssetsByTransferOrTransfereeAxis
| Qualitative and Quantitative Information, Transferor's Continuing Involvement, Transferred Financial Assets, by Transfer or Transferee [Axis] |
| us-gaap:QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTransferredFinancialAssetsByTransferOrTransfereeAxis |
| Information related to the transferor's continuing involvement in transferred financial assets providing, at a minimum, information allowing for an assessment of the reasons for the transferor's continuing involvement, the risks related to the transferred financial assets to which the transferor continues to be exposed, and the extent of change to the transferor's risk profile due to the transfer (including, but not limited to, credit risk and interest rate risk). Such information may be provided by transfer (a description of the transaction uniquely identifying from other transfers of financial assets of the entity in which the entity maintains continuing involvement) or by transferee (for example, identification of a variable interest entity in which the entity has a variable interest and continues to have involvement with the financial assets transferred). |
| cm:Axis |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTransferredFinancialAssetsByTransferOrTransfereeAxis |