cm:Concept: us-gaap:LessorOperatingLeasePaymentsToBeReceivedRollingYearFour
| Lessor, Operating Lease, Payments to be Received, Rolling Year Four |
| us-gaap:LessorOperatingLeasePaymentsToBeReceivedRollingYearFour |
| Amount of lease payments to be received by lessor in fourth rolling twelve months following latest statement of financial position date for operating lease. For interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:LessorOperatingLeasePaymentsToBeReceivedRollingYearFour |