cm:Concept: us-gaap:ContractWithCustomerAssetChangeInMethodCreditLossExpenseReversal
| Contract with Customer, Asset, Change in Method, Credit Loss Expense (Reversal) |
| us-gaap:ContractWithCustomerAssetChangeInMethodCreditLossExpenseReversal |
| Amount of expense (reversal of expense) for expected 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, from change in methodology. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:ContractWithCustomerAssetChangeInMethodCreditLossExpenseReversal |