cm:Level3TextBlock: us-gaap:ContractWithCustomerAssetAllowanceForCreditLossTableTextBlock
| Contract with Customer, Asset, Allowance for Credit Loss [Table Text Block] |
| us-gaap:ContractWithCustomerAssetAllowanceForCreditLossTableTextBlock |
| Tabular disclosure of allowance for credit loss on right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ContractWithCustomerAssetAllowanceForCreditLossTableTextBlock |