cm:Concept: us-gaap:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerSharePlannedSaleInvestmentsNotIdentifiedDescription
| Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Planned Sale, Investments Not Identified, Description |
| us-gaap:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerSharePlannedSaleInvestmentsNotIdentifiedDescription |
| Description of remaining actions required to complete the sale or liquidation of an investment in certain entities that calculate net asset value per share, including, but not limited to, by unit, membership interest, or other ownership interest, but has not yet identified the specific investment to be sold or liquidated. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerSharePlannedSaleInvestmentsNotIdentifiedDescription |