cm:Level3TextBlock: us-gaap:ScheduleOfNetAmountOfRiskByProductAndGuaranteeTextBlock
| Schedule of Net Amount of Risk by Product and Guarantee [Table Text Block] |
| us-gaap:ScheduleOfNetAmountOfRiskByProductAndGuaranteeTextBlock |
| Tabular disclosure of the guaranteed benefits in excess of the current account balance, quantifies such excesses (the net amounts at risk) and includes other relevant, pertinent information as of the most recent balance sheet date by product type. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfNetAmountOfRiskByProductAndGuaranteeTextBlock |