cm:Concept: us-gaap:SecuritiesFinancingTransactionsAccountingPolicy
| Securities Financing Transactions, Accounting Policy |
| us-gaap:SecuritiesFinancingTransactionsAccountingPolicy |
| Disclosure of policies related to how securities financing transactions are recorded on the balance sheet including the recording of fees received and paid and under what circumstances receivables and payables amounts are offset. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:SecuritiesFinancingTransactionsAccountingPolicy |