cm:Level3TextBlock: us-gaap:ScheduleOfPropertySubjectToOrAvailableForOperatingLeaseTextBlock
| Schedule of Property Subject to or Available for Operating Lease [Table Text Block] |
| us-gaap:ScheduleOfPropertySubjectToOrAvailableForOperatingLeaseTextBlock |
| Tabular disclosure of lessor's property under leasing agreements and property available for lease (not currently under lease) by property class, the gross amount, accumulated depreciation and net amount of as of the balance sheet date. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfPropertySubjectToOrAvailableForOperatingLeaseTextBlock |
| PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClass |