cm:Table: us-gaap:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable
| Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] |
| us-gaap:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable |
| Disclosure of information about investments in certain entities that calculate net asset value per share or equivalent measured at fair value on a recurring or nonrecurring basis. |
| cm:Table |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable |