cm:Level3TextBlock: us-gaap:FairValueByBalanceSheetGroupingTextBlock
| Fair Value, by Balance Sheet Grouping [Table Text Block] |
| us-gaap:FairValueByBalanceSheetGroupingTextBlock |
| Tabular disclosure of the fair value of financial instruments, including financial assets and financial liabilities, and the measurements of those instruments, assets, and liabilities. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:FairValueByBalanceSheetGroupingTextBlock |