cm:Member: us-gaap:FairValueOptionElectionForVariableInterestEntityMember
| Fair Value Option Election for Variable Interest Entity [Member] |
| us-gaap:FairValueOptionElectionForVariableInterestEntityMember |
| Related effect on line items in the statement of financial position from the cumulative-effect adjustment to retained earnings as a result of electing the fair value option for a variable interest entity or a group of variable interest entities. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:FairValueOptionElectionForVariableInterestEntityMember |