cm:Concept: us-gaap:VariableInterestEntityFinancialOrOtherSupportType
| Variable Interest Entity, Financial or Other Support, Type |
| us-gaap:VariableInterestEntityFinancialOrOtherSupportType |
| Description of the type of financial or other support (for example, liquidity arrangements and obligations to purchase assets) provided by the reporting entity to the Variable Interest Entity (VIE) which the reporting entity was not previously contractually required to provide or that it intends to provide. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:VariableInterestEntityFinancialOrOtherSupportType |