cm:Concept: us-gaap:NetAmountAtRiskByProductAndGuaranteeNetAmountAtRisk
| Net Amount at Risk by Product and Guarantee, Net Amount at Risk |
| us-gaap:NetAmountAtRiskByProductAndGuaranteeNetAmountAtRisk |
| Net amount at risk, representing the guaranteed benefit in excess of the current account balance corresponding to the specified product, guarantee type and subset of the guarantee. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:NetAmountAtRiskByProductAndGuaranteeNetAmountAtRisk |