cm:Concept: us-gaap:FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
| Financing Receivable, Troubled Debt Restructuring, Subsequent Default |
| us-gaap:FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 |
| Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 |