cm:Level2TextBlock: us-gaap:RevenueRecognitionAccountingPolicyGrossAndNetRevenueDisclosure
| Revenue Recognition Accounting Policy, Gross and Net Revenue Disclosure [Policy Text Block] |
| us-gaap:RevenueRecognitionAccountingPolicyGrossAndNetRevenueDisclosure |
| Disclosure of accounting policy for recognizing revenue from a transaction on a gross or net basis. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:RevenueRecognitionAccountingPolicyGrossAndNetRevenueDisclosure |