cm:Concept: us-gaap:FairValueOptionElectionForVariableInterestEntityReason
| Fair Value Option Election for Variable Interest Entity, Reason |
| us-gaap:FairValueOptionElectionForVariableInterestEntityReason |
| A description of management's reason for electing the fair value option for a particular variable interest entity or a group of variable interest entities as well as a description of the reason for different elections if the fair value option is elected for some variable interest entities and not others. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:FairValueOptionElectionForVariableInterestEntityReason |