cm:Concept: us-gaap:CreditDerivativeLiquidationProceedsMonetaryAmount
| Credit Derivative, Liquidation Proceeds, Monetary Amount |
| us-gaap:CreditDerivativeLiquidationProceedsMonetaryAmount |
| Estimated amount to which the maximum potential amount of future payments under the credit derivative would be covered by the proceeds from liquidation of assets held either as collateral or by third parties. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:CreditDerivativeLiquidationProceedsMonetaryAmount |