cm:Member: us-gaap:CumulativeEffectAdjustmentDeconsolidationOfVariableInterestEntityMember
| Cumulative-Effect Adjustment, Deconsolidation of Variable Interest Entity [Member] |
| us-gaap:CumulativeEffectAdjustmentDeconsolidationOfVariableInterestEntityMember |
| Represents the cumulative-effect adjustment on retained earnings for deconsolidation of a variable interest entity or group of variable interest entities upon application of new accounting guidance. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:CumulativeEffectAdjustmentDeconsolidationOfVariableInterestEntityMember |