cm:Concept: us-gaap:ContractWithCustomerAssetAllowanceForCreditLossWriteoff
| Contract with Customer, Asset, Allowance for Credit Loss, Writeoff |
| us-gaap:ContractWithCustomerAssetAllowanceForCreditLossWriteoff |
| Amount of writeoff of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, charged against allowance for credit loss. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:ContractWithCustomerAssetAllowanceForCreditLossWriteoff |