cm:Concept: us-gaap:OperatingLeasesOfLessorContingentRentalsDescriptionOfVariableRateBasis
| Operating Leases of Lessor, Contingent Rentals, Description of Variable Rate Basis |
| us-gaap:OperatingLeasesOfLessorContingentRentalsDescriptionOfVariableRateBasis |
| The reference rate for the variable rate of the lessor's operating lease, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:OperatingLeasesOfLessorContingentRentalsDescriptionOfVariableRateBasis |